Done. I think g6 is the best choice, intending Kg7 and making f7 less vulnerable.
To the game: http://www.chess.com/votechess/game.html?id=14051
To the Alliance: http://www.chess.com/groups/forumview/move-28-the-conditional-move-thread?

What a pity. The choice fell on Rb4 which was the most expected one. Still it interesting how many choices White had. It is also interesting to follow the Black struggle for survival and how important it is to keep fighting in what can feel like a hopeless position.
So we are back to this:
"26. ... Rb8 27.Be2 (Threat:Bxa6) Rc6 28.Rb4 Bd8 29.Qd5 (Threat:Qxe5)(29.Qa4 (Threat:Bxa6) Rbc8) and the Black Queen must move. Some interesting pressure play here. White is expanding her area of influence, so besides keeping Black busy on the queen wing something is slowly building up against the king side. Just think Bc4 and Rd1-d3-f3." ( Comment move 26 )
As I can judge, the black rooks are locked. Moving Rc6 allows Bxa6 and moving Rb8 means a sell out of the b-pawn. The black queen have some options but the focus will be on the counter strike Bd8 or "Luft" (The first time I saw that word was in Fischer's, My 60 Games.) for the king. White will probably want to play Bc4 next and any Black answer now will also include the best answer to that.
dsarkar had a line that went:
I think there might be some weak spots but it is interesting to see that the main line proposed looks like my sac line suggested at Black's move 18. The conclusion that White looses tempo with 33. ... is wrong I think, since 34.Qb3 would be a natural choice anyway. The other lines looks a bit messy and it can't be Black's best. The red line also holds some improvements for White.
Candidates:
28. ... Bd8 29.Qa4 Rbc8 (Old moves) 30.h3 We are back at the Bg4 idea. ... Qc7 31.Qb3 The black queen is the sole defender of b7 and I dont believe in Qxa5 Rxb7. 31. ... b5 will also generate the same position. So 31. ...Rb8 Back again. 32.Bc4 Heading for d5. White keeps working for the optimal spots. Maybe b5 here but it will generate a weak a-pawn and f7/d6 are still vulnerable.
28. ... Be7 The lame threat d5 is easily met with Bc4.
28. ... Kf8 The same reasons as for g6.
28. ... g6 Might not be bad at all since most of Black choices are limited. It is also a way to eventually move the f7-pawn after Kg7.
28. ... h6 It feels more natural to have the pawns on the opposite colour. So if there is a choice between g6 and h6, g6 for sure.
28. ... Qc7 Attacking the a-pawn but if it means trading the b-pawn White is better, so White can continue the build up with the bishop move. 29.Bc4 Now if Bd8, then Bd5. 29. ... b5 maybe. 30.axb6 ( I looked earlier on lines like Bd5 Rc5 Ra1.) ...Rcxb6 31.Rxb6 Rxb6 32.Qa2 I have a hard time seeing this is not good for White with the backward d6 and the iso on a6. White's king and b2 is vulnarable just now but there is time to remedy it. I believe all Qc7 lines to be inferior.
As Black I think I would go for g6.