There are a few ways to stream video from your computer to your TV. Among them are the Windows Media Center + Extender way and the wireless media streaming way. Add to these the DMP300 Digital Media Player way for Viiv.
By hooking this up to your TV via composite/S-Video/component/HDMI, you can stream MPEG1/2/4, WMV and XviD straight from your PC to the DMP300, which decodes on the fly. Not only that, it's got 802.11 b/g for wireless-ness, in case there's no 10/100 ethernet cable able to reach your TV.
No availability or price on this yet.