Peter Gulutzan, who I had the pleasure of meeting (and eating) with a number of times at the developer’s conference in Sorrento, has written a very good overview of the new MySQL Events features plugged into MySQL 5.1.
Events differ from triggers because you can set an event to happen at a specified time or a specific interval. Although sometimes referred to as CRON for MySQL, events are slightly more flexible, and database driven making them much more practical than running a script or other tool through the cron, at or similar tool.