By appearances, 1...c5 doesn't seem to accomplish nearly as much as White's opener, 1.e4.  Black will need to make at least two more pawn moves to release both bishops and three moves to get castled, while the Black king's residence in the center will carry its own risks.  Thus White's most ambitious approach is to "gambit" a central pawn for undefined but rather long-term attacking chances, via the mainline with 2.Nf3 and 3.d4.  However, the typical streetfight after opposite-sides castling is not to every 1.e4 player's taste. 

In addition to contesting d4 immediately with 2.c3, White has a number of "closed" setups that more or less ignore Black's control of d4 for the time being.  White can play the Closed Sicilian, Grand Prix, "Big Clamp", 2.Na3!?, or King's Indian systems.  One of the more radical options is 2.a4!?!? which must be proof that being White means being able to get away with virtually anything short of losing material.  It appears the basic idea of 2.a4 is to meet any a7-a6 with a4-a5 to clamp down on b6, and to meet Nc6 or d6 with Bb5 in order to direct play into Rossolimo channels where the a4-pawn, by defending White's bishop, is not so ridiculous. 

FM Stefan Buecker has published an interesting article featuring 2.a4!?!?, and started a messageboard discussion including a commented PGN of the following game.  I am sure that after skimming the linked sources, you will "know" more about this quirky opening than any Sicilian player in a 100 mile radius.

For a super-lean repertoire, 2.a4 looks  like an interesting option for those who would like to take up 1.e4 in an afternoon or to prepare an anti-Sicilian in a single sitting.  I note that FM Buecker has also published on offbeat repertoire lines in the Open Game, French, Caro-Kann, and Pirc/Modern.  While on this topic, I should mention that the Kenilworthian also has articles on, e.g., the French "Monte Carlo variation" and the Caro-Kann "Apocalypse Attack", that could serve the same purpose.

I ran an engine match between Stockfish and Critter on my old 32-bit laptop.  Stockfish won the match, but Critter won the first game in a model demonstration of a central pawn majority in the QG exchange variation.  This was the best game of the match, although marred by Black's aimless shuffling with the king and knights.  Critter's play however appears very "human" and strategically clear.

Style-wise I find that Critter plays like Topalov and seemed to sac an exchange in virtually every other game.  Critter finds much more dynamic compensation than Stockfish, making Critter extremely useful for analysis.  I am also impressed with both engines for their efficient use of system resources.  Stockfish uses in general half as much RAM as Houdini, and Critter uses half as much RAM as Stockfish.  Additionally, on both of my computers (old/XP and new/Windows7), Houdini continues to throttle the CPU at 100% if the GUI is closed while the engine is running.  Because of this I have actually removed Houdini from my computers.

The purpose of this article will not be to spell out variations, but to describe an organizational approach to studying and managing a serious queen-pawn repertoire.  Black's defenses in terms of quality and frequency can be grouped into three tiers. 

First Tier, 60-70% of your games and study time:

1.  KID / Benoni, Hungarian, Seirawan (Bd3), or Four Pawns
2.  Nimzo, Reshevsky
3.  QGD, Exchange (pt.1, pt.2, pt.3, pt.4, pt.5)
4.  Slav, Exchange

Defenses in the First Tier are common enough to justify playing a relative mainline.  Proponents of these venerable defenses are usually very experienced to have seen everything before and not to fear big theory.  To promote efficiency I only considered anti-KID variations that apply equally to the Benoni so as to kill two Angry Birds with one stone.  I also settled on the Exchange Slav to avoid the labyrinthine Slav and SemiSlav.

Second Tier, 20-30% of your games and study time:

5.  Dutch, 2.Nc3
6.  Grunfeld, Romanishin
7.  Benko, Dlugy attack 5.f3
8.  QGA, 3.e3

The Second Tier defenses tend to inspire fanatical devotees at the club level, who thanks to excellent repertoire materials for Black tend to be fairly knowledgable and booked up.  So I purposely went for sidelines that strike me as being atypical for the opening and/or easier for White to play intuitively.

Third Tier, 10% of your games and study time:

9.  Budapest / Fajarowicz gambit (pt.1, pt.2)
10. Tarrasch / Schara gambit
11. Chigorin / Albin gambit
12. Baltic

The Third Tier defenses generally rely on early tricks and/or early confrontation in the center.  As a result, the play is generally very forcing from the get go, meaning that Black has few ways to deviate from established lines without just being clearly worse.  In turn, it is relatively practical to prepare a reliable line fairly deeply since Black's responses are predictable and limited.

Topalov ventured against Kamsky the obscure Romanishin line with 7.Bf4 against the Grunfeld in their Candidates game today.  I have mentioned this very same (rare) variation at this blog!  Topalov deviated from Schiller's recommendation (feels surreal to type that, yes) by going 8.Qa3 instead of 8.Qc2.  (See Schiller's e-book at the top of page 3.)  Of course, Topalov's further experiment of 0-0-0 and h2-h4 amounted to either wishful thinking or disrespect against a lionhearted defender like Kamsky.

Also see GM Henrik Danielsen's video analysis of the game at chessdom.com

I've updated my White repertoire against the Nimzo-Indian, based on the method of the positional Nimzo assassin, Sammy Reshevsky.  After 1.d4 Nf6 2.c4 e6 3.Nc3 Bb4, I want to play simply 4.e3 intending Nge2 and a3.

I am happy to publish the following e-book of annotated games, date-stamped in case I decided to supplement or revise it in the future.

Below is an opening outline to sort out Black's fourth-move options, and the links go to illustrative game examples.

Nimzo, Rubinstein 4.e3, Reshevsky plan
    A.    4...b6 5.Ne2
        1.    COBE 5...Ba6 6.Ng3 Bxc3+ (6...0-0?!) 7.bxc3 d5 8.Ba3 Bxc4 (8...dxc4?) 9.Bxc4 dxc4
            a.    Endgame line 10.Qa4+
            b.    Gambit line 10.e4 or 10.0-0
        2.    Romanishin-Psakhis 5...c5 6.a3 Ba5 7.Bd2 0-0! 8.Rb1 Na6 9.Nf4
        3.    Pseudo-QID 5...Bb7 6.a3 Be7 7.Nf4
        4.    Pseudo-Dutch 5...Ne4 6.Qc2 7.a3 Bxc3 8.Nxc3 Nxc3 9.Qxc3
    B.    Reshevsky variation, 4...0-0 5.Ne2 d5 (5...Re8) 6.a3 Be7 7.cxd5
        1.    Soviet line 7...exd5 8.b4
        2.    Fianchetto line 7...Nxd5 8.Bd2 Nbd7 9.g3
    C.    The IQP line, 4...c5 5.Ne2 d5 6.a3
        1.    Double IQP line 6...cxd4 7.exd4 Be7 8.Nf4
        2.    Karpov’s IQP line 6...Bxc3 7.Nxc3 dxc4 8.Bxc4
    D.    Botvinnik variation, 4...d5 (4...Nc6?!) 5.a3 Bxc3 6.bxc3 0-0 7.cxd5 exd5 8.Bd3
        Khalifman - Bologan, 2002
        Petrosian - Ljubojevic, 1983

Legendary American grandmaster Sammy Reshevsky was a  positionally-minded Nimzo-killer.  I've worked on a complete anti-Nimzo repertoire according to Reshevsky, based on 1.d4 Nf6 2.c4 e6 3.Nc3 Bb4 4.e3 intending simply Nge2 and then a3 with play akin to the Queen's Gambit rather than the ultra-sophisticated Nimzo lines.  This repertoire is new and a work in progress, but I've uploaded my anti-Nimzo repertoire according to Reshevsky.  Or you can snag the PGN below.  This approach seems to me to be classically sound and not overly difficult to play.

I'm new to all this 1.d4 stuff, so I'd love to get feedback from those with more experience/knowledge.

So far I've only found this e-book (PDF) by FM Eric Schiller.  Fortunately, the e-book is quite thorough, although poorly formatted for monochrome printing.  (You'll need color highlighters to mark the nested variations.)

After 1.d4 Nf6 2.c4 g6 3.Nc3 d5 4.cxd5 Nxd5 5.Nf3 Bg7 6.Qb3, Black will decide for White where the c1-bishop will deploy.  (Diagram)

If 6...Nxc3 7.bxc3, the bishop is coming to a3, while if 6...Nb6, White replies with either 7.Bg5 or 7.Bf4 (obviously not fearing 7...Bxd4?? 8.0-0-0).

Keene & Jacobs offer the illustrative game, Tisdall - Jansa, 1983, featuring 7.Bg5, and analyze Schiller's recommendation of 7.Bf4 in the notes.  To my eyes, 7.Bf4 seems more flexible since it helps control both e5 and c7.  I will edit this post as I find more resources on this line.

I am a big fan of GM author Jacob Aagaard, yet his Starting Out: The Grunfeld is harshly dismissive of this variation, which he writes off in a single sentence.  Yet, it's not clear-- to me anyway-- why the power of the Russian and Exchange systems should be entirely lost on this hybrid that combines features of the two.  In any case, this fairly straightforward variation was the frontline choice for GMs Romanishin and Tisdall, and IM Remlinger of course.

I've been helping a friend nail down a 1.d4 2.c4 repertoire based mainly on recommendations of An Opening Repertoire for White by Keene and Jacobs.  In the process, I've "accidentally" been learning the same systems.  Originally, I intended to investigate the ubiquitous Zukertort-Colle, a.k.a. "the club player's meth habit", but the damn thing struck me as quite odd, unwieldy, and counterintuitive.  So I turned to the suggestions of Keene and Jacobs, which flow rather nicely, have some practical sting, and could even serve as a frontline repertoire for an I.M. or G.M.  In fact, the book appears to be based on the real-life repertoire of pentagenarian IM Larry Remlinger in the early 1990s.

Those who venture 1.d4 2.c4 must reckon with the mighty King's Indian Defense.  As GM Forintos observed, the K.I.D. typically inspires a "Man Or Mouse" decision, as White usually either wagers his King's safety in order to overrun Black's queenside, or plays like a mouse.  The so-called "Hungarian variation" ("Kramer System" sounds weird to me, and "Attack" too promotional) in the King's Indian Defense starts with 1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.e4 d6 5.Nge2, intending 6.Ng3.  It may seem odd to move the KN twice by move six, but the knight supports a potential h4-h5 rush, defends the e4-pawn against knights on f6 and c5, and eyes the critical King's Indian square, f5.  Most importantly, the knight's presence on g3 means that a Black pawn won't be arriving there to supervise a Bxh3 sacrifice.
.

So here are the web references:  As a starting point, it would be difficult to outdo the fantastical game, Serper - Nikolaidis, 1993 for inspiration and imagination.  For sheer enthusiasm, check out IM Tim Taylor's effusive commentary on the stereotyped Bxh5 sacrifice, and his equally personal account of a second game at JeremySilman.com.  GM Valeriy Neverov (2571) crushed the lovable GingerGM in an annotated game from Hastings 2008 (replayable here).   GingerGM offers a critical view of the opening in this game (and video).  More White-biased games are found in this useful games collection.  For the Benko-style variant, see this game by GM Grigory "U." Serper, and refer to GM Yermolinsky's comments on pages 97-100 of The Road to Chess Improvement.  Finally, NM Abby Marshall has outlined the variation from a more neutral perspective in her monthly column (archived as PDF).

Interested persons may also wish to purchase the favorably-reviewed book on this variation for less than Two Dollars (< $2.00) from Strand.