The Studio TVR will do that, but the cheaper Studio DV will do it as well. The format will be .dv, so it can be used in iMovie.
The Dazzle Hollywood and Canopus ADC-something will do it as well.
You might want to look into eyeTV. It uses USB and records the video as an mpg file.
Also, if you have a digital camcorder with A/V pass-through, you could use it as a DV bridge (like the Formac, Dazzle, or Canopus units). The only problem is that you might run into problems with Macrovision if you're trying to import commercial DVDs and VCR tapes.
