StealthPoop

Wired News: Sneaky Toolbar Hijacks Browser:

"Xupiter is an Internet Explorer toolbar program. Once active in a system, it periodically changes users' designated homepages to xupiter.com, redirects all searches to Xupiter's site, and blocks any attempts to restore the original browser settings."

I got hit by this one while approving ads for work. Suddenly, you get a really ugly toolbar in IE, complete with scrolling text. It's like an ad for a crappy BBS has been appended to your browser.