I alternate between "Cheers," and "Cheers!" as a closing.

Personally, I picked it up from a bunch of Canadians I worked with. They used it in their e-mails. In my mind, it's most closely related to the drinking toast. I've never heard the T.V. thing mentioned by the Anonymous Monk, although I watched the show for quite some time.

Cheers!

Brent
-- Yeah, I'm a Delt.