Where is Simon from jazzwise when you need him?
There is a great bit of software you can but quite cheaply for an iphone or an ipod touch.
It is a Real Book, but better than that, you can type in the key you want the tune to be in and it tranposes the music there and then!
I've yet to buy this software, as I think it could make me lazy, but I've been on a gig with a baritone player who was using it.
The beautiful thing is, it's small; in fact, it fits in your phone.
I think I'm getting a touch of GAS. Where did I put the antacids?