PVR Card Identification Guide
If you are shopping for a TV recorder for your PC, this guide from Home Theater PC News should answer just about any question you have, as well as compare cards by what they look like, say if you are buying one on eBay but the seller doesn’t have much info about it other than a picture.
If you use a Mac there are options like the AlchemyTV PCI Card (Power Macs only) and the EyeTV (USB/Firewire). I have the original USB EyeTV and use it with my eMac all the time. It really does change the way you watch TV!