I am currently running Ubuntu as my primary desktop and have enjoyed it greatly, I especially like the variety and quality of screensavers available.
However, due to work requirements, I am switching back to a Windows desktop (SSTP VPN, RDP Gateway, etc…) and am really going to miss being entertained by the screen savers when I go get some coffee.
I found http://www.reallyslick.com/index.html which appears to have ported several of the savers to windows. At first I was hesitant (can you say virus), but ran them through several scanners and they seem to be working fine. Not all of the savers are included (bouncing cow), but its enough of a variety to keep me happy for now.