Lines given by stormcrow contain ideas with a3 for Black.

I add these ones with a quick c3:
- 1.e4 e6 2.d4 d5 3.Nd2 Be7 4.c3!? Nf6 5.e5 Nfd7 6.Ngf3 c5 7.a3!? Rozentalis-Ivanov,Halkidiki 2002 then 7..a5!? (otherwise 8.b4)
- 6.Bd3 c5 (if 6...b6 then 7.Qg4) 7.Ngf3 Nc6! (7...b6?! Tkachiev-Bauer,N1 2002 (EE juin 2002) and Smirine-Pelletier,Bienne 2002 (EE septembre 2002) 8.Qe2! Nc6 9.a3! and advantage to White in Rogic-Levacic,Porec 1994 (Psakhis Nd2) or 8...a5 9.c4! or 8...cxd4! (best) 9.cxd4 a5 10.Nf1 Ba6 11.Bxa6 Nxa6!? Ehlvest-Lputian,Manille 1990 (Psakhis Nd2))  8.oo 

In the position after 8.oo, the move a5 is only a "useful waiting move" because:
A) 8..g5 9.Bb1! or 9.a3!? Qb6 10.dxc5 Nxc5 11.Bc2 g4 12.Nd4 Nxe5 13.b4 Vajda-Ionescu,Tusnad Roumanie 2005 
B) 8...cxd4 9.cxd4 g5 10.Nb3 a5 11.a4 and advantage to White or 9...Qb6 10.Nb3 a5 11.a4 Nb4 12.Bb5 oo 13.Re1 Qd8 14.Bf4 Nb8 15.Rc1 and White is better. Rachels-Short,Manille 1990 (Psakhis  Nd2) or 9...Nb6 10.Re1 a5 11.Nb1! Smirin-Bauer,Saint Vincent 2000 (Psakhis Nd2)
C) 8...Qb6 9.dxc5! Qc7 10.Nb3 
D) 8..f5 9.exf6 Cxf6 10.dxc5 Fxc5 11.b4 Fd6 12.b5 Ce5 13.Cxe5 Fxe5 14.Fb2
E) 8...oo 9.Re1 Qb6 10.c4 cxd4 11.cxd5 exd5 12.Nb3 f6 or 10.Nf1 cxd4 11.cxd4 g6!? 12.Bc2 f6 13.exf6 Nxf6 14.Ba4 Ne4 Nedev-Lputian,Istambul 2000 (Psakhis Nd2)
F) 8...h5 9.Re1 g5 10.dxc5!? Emms-Lalic,Southend 2001 (Psakhis Nd2) or 9...cxd4 10.cxd4 g5 11.Nb3 g4 12.Nfd2 a5 13.a4 Qb6/Nb6 14.Nb1! 

TopNotch wrote on 12/23/06 at 20:40:28:


Finally I have found time to do a little research and I am afraid I don't agree. Even with a lost tempo White can adopt a similiar strategy:

1.e4 e6 2.d4 d5 3.Nd2 Nf6 4.e5 Nfd7 5.c3 c5 6.Ngf3 (or 6.Bd3 - idea Nc6 7.Ngf3 - b6 7.Nh3!?) Be7 7.Bd3 b6 8.Qe2 a5 9.a4 Ba6 10.Bb5 or 9.o-o Ba6 10.c4!?
1.e4 e6 2.d4 d5 3.Nd2 Be7! 4.Ngf3 Nf6 5.e5 Nfd7 6.c3 c5 7.Bd3 b6 8.Qe2 is the same.
So this strategy does not solve all Black's problems.

Thank you Stormcrow and Topnotch; you're posts were both very enlightening to me!  I'm considering taking up the French, so this is all of interest.

It is useful to know that the move order: 1.e4 e6 2.d4 d5 3.Nd2 Be7! 4.Ngf3 Nf6 5.e5 Nfd7 6.Bd3 (6.c3 c5 7.Bd3 transposes) c5 7.c3 b6! is a very effective antidote for Black against the Korchnoi Gambit/Universal System. Here Black intends the positionally desireable exchange of light squared Bishops via a6 and when compared to similar positions in the Korchnoi Gambit it is clear to see that White has committed his Bishop to d3 too early. The question then becomes, can white favorably avoid committing his light squared bishop prematurely? 

[Event "Korchnoi Birthday KO"]
[Site "Zurich SUI"]
[Date "2001.??.??"]
[White "Kasparov,G"]
[Black "Short,N"]
[Round "2.1"]
[Result "1-0"]
[WhiteElo "2827"]
[BlackElo "2676"]
[ECO "C07"]

1. e4 e6 2. d4 d5 3. Nd2 c5 4. Ngf3 Nf6 5. e5 Nfd7 6. c3 b6 7. Bb5!! Be7 [Alternatively if 7...a6 White simply retreats the bishop to d3 thus thwarting the exchange of light squared bishops. If Black insists on an exchange with 7...Ba6 then White agrees, but on his own terms with 8.a4, ensuring that if Black exchanges he will be left facing unpleasant pressure on the a file] 8. O-O O-O 9. Re1
a5 10. Nf1 Ba6 11. a4 Bxb5 12. axb5 Re8 13. Ng3 Nf8 14. Nh5 Nbd7 15. g3 Ng6 16. h4 Ndf8 17. Kg2
Qd7 18. Bh6 gxh6 19. Qd2 f5 20. exf6 Bd8 21. Qxh6 Ra7 22. Ng5 Qxb5 23. f7+ Rxf7 24. Nxf7 1-0

The above game represents model play against this early b6 line in the Tarrasch, however it is not as effective against the 3...Be7 variation since White finds himself a tempo down if he tries to implement the same strategy.   

Definitely food for thought.

Toppers

I know absolutely nothing about these positions.  I have played them with neither White nor Black; however, I was curious about the move a5 as well, wondering what its uses might be.  After glancing at the PDF eBook on this site for 10 minutes, I saw some ideas.  Here's what I can deduce about a5...

As black's natural realm for counterplay (based on the pawn chain) is the q-side, a5 is a logical development in that area.  Not only does it gain space and prevent white from expanding there, it also has the possibility of driving further into the position and creating weaknesses and opening some lines.  The a8 rook might be good where it initially stands. 

It also relates to the fight in the centre.  Delaying or avoiding Qb6 allows black to respond to dxc5 (which would hit the queen) with the ...Ndxe5.  Or, black may want to pressure white's centre w/ Qb6.  Here a5 is useful because if white tries to fortify d4 with Nb3 he's hit with a4. 

If white meets a5 with a4, then Black can develop in the following manner: cxd4, Nb4, Be7, 0-0, Nb8, N8c6, Bd7, Rc8, etc...If white sticks a bishop on b5, black can try to swap it with Bd7, or harrass the bishop with the rerouting Nd7-b8-c6-a7 (a square which is freed up from a5).   

Of course many of these plans on the q-side are combined with agressive intentions on the k-side with f6 and/or g5.  The planning and timing must be subtle, though, in order to successfully snatch the initiative.

In the a5 lines that include an early Be7, black might go for a plan favored by Korchnoi:
initiating a q-side pawn storm with c4 and b5, leaving the king in the centre, and closing off the kingside as necessary with h5 and g6.

I also wish I understood the move ...a7-a5 in these positions.  If White has played a3, then I see the point of playing ...a5; it stops b2-b4 and Black may go on with ...a5-a4, clamping down on some juicy squares.  Before White has played a3 though, I don't really understand the move (unless Black is preparing for ...Nb4).  A case in point: I wish someone would explain why 8...a5 is so effective in the following line:

1.e4 e6 2.d4 d5 3.Nd2 Be7 4.Ngf3 Nf6 5.e5 Nfd7 6.Bd3 c5 7.c3 Nc6 8.0-0 a5

Is Black really threatening to attack the base of the pawn chain on b2?  Is this some sort of waiting move?  I don't really get it in this particular position.

Cool, I worked out a line in a book!

Can someone tell me why ...a5 appears in a lot of these variations? What is the point?

I think you'll find that Neil McDonald recommends this line v French in his book Starting out 1e4 !

Very dangerous for the unprepared and even the prepared !

Andrew