I received an email this evening announcing that SharePoint Experts has just released PowerUndelete for WSS:

"Whenever someone deletes a list item, or a document from a document library, PowerUndelete captures it and stores it in an "Undelete bin". End users are empowered to "undelete" their own documents, saving the support desk from the trials of recovering files and list items from database backups."

Very cool - this is promising stuff. I have not been able to try it yet (but may do so once I can see it in action). A video demo showing the product will be made available within the next day or two. You can get more information on the SharePoint Experts web site. They have a few different add-on enhancements available for SharePoint.