A subtle tactic was sprung on me from this position at a recent tournament by my Uncle and I thought it was pretty cool. Can you find it? 

b4 is looking pretty good

axb4 and what now?

1. b4 axb4 2. axb4 Bxb4 and the pin screws white right up.

whatever the tactic is, i cant see it but it must be awesome :P

what about rd6??

Perhaps 1. b4 axb4 2. axb4 Bxb4 3. Rxd8, with either...
  3... Rxd8 4. Rxd8 Qxd8 5. Qxb4, or...
  3... Bxc3 4. Rxa8 Bxb2 5. Rxe8+ Qxe8 6. Nxe8

I'm probably missing something though. :\

I considered Rd6, sacrificing the exchange to open the a1-h8 diagonal, with discovered check tactics, and possibly mating threats.

I don't think black can decline, because the Bc5 will be forced to take after 2. b4 axb4 3. axb4.

A possible variation (though I haven't looked at this very long), 1. Rd6 Bxd6  2. exd6 Qg7  (2 ... Rxd6  3. Nxe8+ Kg8  4. Nxe6)  3. Nxe8 Qxc3  4. Bxc3+ Kg8  5. Nf6, after which white has two pieces for the rook, and with all the pawns still on the board and the bishop on the long diagonal, the two minor pieces should outplay the rook.

What did you actually play?

Well done. You guys nailed it.

Just one thing though honorflamingo: on move 5 Black can play Nc7 instead, winning another pawn.

Your line. Believe it or not he actually blundered soon after and I got a lucky win. 

I think you are missing something, Black can just play 1.Rxd2.

Oh, duh. Serves me right for trying to do this at work. At least this fulfills my making-myself-look-stupid quota for the day before lunch.  :\

Rd6 is d best move here

Wow, Rd6 is nice.