I heard of an interesting utility on MacBreak Weekly podcast recently. It's called Cache Out X and it does a great job of cleaning out all those stupid cache and swap files that show up mysteriously when you start your Mac and your trash is suddenly full. This application handles both system files and internet files that take up useless drive space. It handles 8 different web browsers and has loads of automated preferences, you can even schedule it to run via iCal. Best of all, it's FREE! I found it at versiontracker.com