Giving a pawn in the hope that somewhere  in the future white will miss a 1-move threat is called hope chess and rarely works...the point of b5 is not in a future fork, black simply wants the bishop off the dangerous c4-f7 diagonal. That said, 4...d5 looks like a more logical way to give back the pawn fot the already explained reasons; i don't think 4...b5 is a good move (It's fair to say that Kasparov once played 4...b5 in a rapid game against Short, so it has a strong  (one time) supporter, but it's also fair to say that the russian lost the game in 15 moves...). In any case think i would try to hold the pawn for now.

g5

How about 4...f5

On an android atm so I'll update with the game later (if somebody doesn't beat me to it).

I know d5 isn't a art of much theory and is very rare, but it has grown on me so I'm going with it.

4...d5?!

I don't like the 4...d5 move, but I am curious to see how it plays out.

I would say that White should just ignore the attack on the Bishop (for now) and get aggressive by developing a piece and launching an attack of his own on the Queen by playing 5.Nf3  

yeah that looks good, makes sence, develops with tempo, and gets center control what's not to like

I think it's better to just 5.Bxd5, Nf3 is not going away anytime soon. It's  harder for black to plan if he doesn't know when the queen will be forced back.

I pretty much know my reply to both suggested moves :D Though I probably wont move immediately if 5.Bxd5 is played.

Sorry guys...been rlly busy lately. Anyways, I'm chopping d5 with the Bishop, I'll post a diagram later.

http://www.chess.com/forum/view/general/chesscom-vs-houdini?page=4

I'm thinking Nf6, any thoughts?

I'm thinking 5...Bc5 and throw some pressure on the King side.

Bc5 is met by d4.

of course, 5...Bc5? 6.d4 is just a loss of time.

Why not play Bg4?

Personally I prefer Nf6, and when the bishop retreats(otherwise Black gets the bishop pair) play Bg4. Try to gain time by attacking the queen. After Nf6 Bb3 Bg4 Black has already equalized due to his lead in development. 

After Nf6 im expecting 6.Nf3,not a bishop move.

I dont expect my dark bishop to go past d3 anytime soon,since it could/would be pushed afterwards.

5... Nf6