Here's another one that might be old news to you that I just found out about. Do you guys know about woot.com? It's a web site that sells only one product per day. The product changes everyday. Usually, the item is for sale at a pretty discounted price.
For example, today's item in an 802.11g PCMCIA wireless card for $10. That's pretty good.
Anyway, you never really know what is going to be for sale on any given day or how quickly they will sell out - the site only stocks a very finite quantity each day. It's probable that the item will sell out, especially on days when there is a particularly good deal.
There is also a "side deal," which is a second item for sale alongside the main item - today, it's a Gateway computer for $350.
The site has an RSS feed, so if you want to keep an eye on the deals, just add it to your aggregator (news reader)!