Unable to put weight on foot -- exercise ideas?

I injured myself pretty badly at the beginning of summer, and the healing process is slow. It could be another year before I can do any weight-bearing exercise. At this point, I can stand for about 30 minutes or walk for about 15 before I end up with severe pain that lasts at least a day or two. I'm in physical therapy, and that was helping until I had a major setback two days ago that put my pain back to where it was in June when I couldn't stand or walk at all without pain.

At first I gained about ten pounds simply because I ate the same amount but wasn't exercising. I've since fixed my diet to match my nonexistant activity level, so the weight thing is under control. My concern is my muscles and my cardiovascular system. Neither are getting much use right now, and that's no good. About the only exercise I can think of to do is Pilates mat since that puts no weight on the feet, but I'm getting kind of sick of it. I would like to start working on upper body strength, and I think machines might be okay (I definitely can't lift free weights right now!), so I'll run that by my doctor. Water aerobics is an option, too, I would think, but the only classes nearby happen while I'm at work. I don't know how to swim, but I think if I can get my hands on a water belt (not sure if that's what they're called), I could jog in the water up and down the lanes at my gym.

That's all I can think of, though. Do any of you have any ideas for exercises that don't put weight on the feet? I'm hoping to go to my next doctor appointment with a long list of options that my doctor can either okay or warn me off. I miss walking (my very favorite exercise) and the options of jogging or dancing or hiking or the elliptical (who would have ever thought I would miss the elliptical?); right now, I need to build new options. If I can do *different* things, then I think I'll be able to stay motivated to exercise.

Thanks for any suggestions you're able to share.