Escape Pod is doing a flash fiction contest, and they’re starting to publish the entries. They’re defined as 500 words or less, and they’ve got 157 entries that they’ll be posting in increments over the next month or so, a new batch every two days.
http://forum.escapeartists.net/index.php?board=97.0
Some great stories so far (batch 1 is up), amazing what people are fitting into so few words! Worth checking out for sure.