I saw something on digg a few weeks ago about a new method of captcha (actually, I don't know if it still would be considered a captcha) that was far better for users and keeping out bots. Basically, it showed you a picture and asked you something like a 5 question multiple choice quiz on very blatant stuff in the picture. Another option was a series of ten pictures and it told you to click on the cat, the dog, the raccoon, and the beaver.
I think both of these would be far better.