My favorite conference-that-is-not-really-a-conference is Pacific Symposium on Biocomputing. The bar to get a paper in is really low, and it's set at a nice resort in Hawaii. The whole conference would just empty out all day so people could go to beaches, etc. It starts on a Friday and ends on a Monday. About the only highlight for me was sitting down at the bar and spontaneously meeting Lynn Conway- "what do you do?" "oh, I worked on VLSI...."