I have a GeForce fx5200, and, even if it's the cheapest model, it has a TV-out connector, and for not much more, you can get it with a dvi connector on top of it. Since I'm fairly sure that dvi->rgb adapters exist, you can plug two monitors. Personally, the monitor+tv combo is enough for me, given that the main use of the second monitor is to watch DVDs on (tv's bigger, and it's in front of the couch).

I think Linux could, if you configure it to run enough display servers (1 per card), display stuff on two screens, reardless of what the bios says is the primary, and I found this for windows:

http://www.digitalroom.net/index2.html
http://support.microsoft.com/?kbid=307873