Two weekends ago, Dean did a presentation for the Puget Sound Small Business Server Users Group. The presentation was on a number of nice little tips and tricks, specifically with Windows SharePoint Services.
One of the major topics that Dean covered was how you can create a recycle bin for SharePoint. The recycle bin is actually really cool. A user deletes a file, and it's removed from the site and shows up in a place in the filesystem.
The tool is a 3rd party tool posted over on the GotDotNet website at SharePoint Tools: Workspace Home.
In order to get the instructions and the files, you have to sign-in at the site and look in the lower right hand quadrant. you want to download the two files marked RecylceBin Installation Manual Build 24, and RecycleBin 1.1 (Build 24).
If you have heavy sharepoint users, this is a great tool that you should definately install on your server to protect the files on your site.