The one unfortunate problem I have with resistance training is that it requires a gym, or at least, a set of fairly pricey disks of iron. Rippetoe's criticism of push ups, sit ups, and other body exercises is that you cannot vary the weight, only number, so you end up not doing much to increase your actual strength. Additionally, I can't really think of any exercises that replicate the squat, which is touted as pretty much The Best Thing Ever^TM. So to me this is an unsolved question relevant to both myself and a few close friends...
Mentioned it to a olympic-weightlifting-inclined friend, he sent me back this. Push ups, leg raises, squats, and pull ups. I have a feeling from what I've read thus far of starting strength what Rippetoe's criticism of the routine would be, but hey, it'll work when you're in a pinch (Or cell)!
I'm very intrested, and may buy the reccomended "starting strength" book.