I had an interesting idea in a dream, and unlike most dream ideas it still made sense when I woke up. When I'm teaching a large lecture, I know there are students who are afraid to ask questions because it feels awkward being that one voice in a hundred. My idea is to provide some sort of interface (maybe a website, or twitter, or sms) to let students send me questions electronically during the lecture. I could respond to them during class itself, or if I don't get to them I could respond to them after class. This wouldn't be in place of raising hands, but an additional channel. What do you think?