Well, I just learned a new one from one of my girl friends who climbs. It's supposed to work your obliques and your middle trapezoids. It's easier to demonstrate than to explain, but I'll try.
You grab a bar that you can do pull-ups and chin-ups with (you know, the rack thingies, a weightroom will usually have one or two) and you grab it in the same position you would to do pull-ups (arms out wide, on the parts of the bar that have downward angles). You then raise yourself so your chin is just above the bar, and you slowly and smoothly move your body from side to side as far as you can go each way. It's quite hard if you've never done it before.
I hope you can make sense of that explanation, because it really works those muscles well.
