There's a lovely variant of the Yaha mass mailing email worm waiting for hung over office workers to foolishly download on the return to work January 2nd. What amazes me is that people actually do download screensavers and other .exes from unsolicited mail. I mean, like, duh! I recall having to completely reinstall a workstation at work because its owner "wanted to see the free game that the e-mail was offering." These people should not be allowed to use a computer.

"Like previous versions of Yaha, the latest variant typically spreads by email with subject lines such as "Enjoy this friendship Screen Saver" and infected attachments with filenames including (Hacker_The_LoveStory.scr, KOF_Sample.exe etc.) A full list is in MessageLabs' advisory and there's more info on the virus in an alert by Finnish AV specialists F-Secure."

More here, here, and here.