The Hauppauge WinTV-HVR-950, a "hybrid" TV tuner (meaning it can tune in over-the-air digital broadcasts or standard cable), normally sells for $79. Dell's Home store has it for just $40.79 plus five bucks shipping. That's after a $20 mail-in rebate, but I reckon Dell's good for it.
Hauppauge tuners are widely regarded as some of the best in the business. The HVR-950 comes with DVR software but also works with Windows Media Center. (Also included: Elgato EyeTV Lite, meaning you can use the tuner with a Mac!) You'll have to supply the antenna if you want over-the-air HD, but as long as you live in a fairly metropolitan area, any cheapo antenna should do.
Regular 'Skaters know of my fondness for tuners like this. Here's your chance to score one of the better models at a bargain price. The rebate offer expires May 21.