You have two different options - a video card with TV-out or a separate scan converter.
For a video card, I like certain ATi cards, depending on how much you want to spend and how much gaming performance you need (all have great 2-D performance). Radeon 64MB ViVo for about $300, All-in-Wonder 128 32MB for about $200, or Rage Fury Pro 32MB for under $100 would all give nice TV-out capabilities.
If you don't really need a new video card, take a look at a scan converter, which connects between your existing video card and TV. The Averkey imicro runs about $90, and is supposed to be fairly good.