I know of a sensei in Boise who only has one arm (Alajandro (sp?)). I ran into him again in Denver at the Saito Sensei Seminar in February. He has great technique, and was quite fun to work with and learn from.
Last year I had a partial seperation in my shoulder. I couldn't do anything for about 6 months and then I've been slowly getting back into action (it really sux!!!!). But since I don't like to sit back all the time and watch others get thrown around (jealousy!!!
), I'd get up and try something. During this time we had some people come in and they were able to show me some one-armed techniques. It was fun, and it taught me a lot about adaptability. You have to get it at your level and then take it beyond!