Check out this hi-res video of a Cessna 182 accidentally landing with the gear up.
I saw this on FL350 and contacted the videographer, Paul Wingo, to get written permission to upload it to YouTube as FL350 doesn't allow video embedding and they have all sorts of scary warnings about how they'll sue the pants off anyone who uploads videos from their site to Youtube or Myspace etc. I repeat, I have written permission from the author, Paul Wingo, to upload this.
This is what Paul said about the flight:
"There was a snow storm approaching in about an hour and we were doing a check ride. Because of possible ice, we had been flying with the gear down the entire time. We started doing touch and goes after a while. Habit when you take off is to raise the gear. This is what happened. So, when we come around, they were conversing and what not and simply forgot the gear was up."
I'm not gonna criticize the pilots at all, because if I do, I am guaranteeing that I'll forget to put the gear down on my next flight.