I bought a Freecom DVB-T (terrestrial digital TV) USB stick for my PC. Then, a few months later, I shelled out for the eyeTV software. Works great with the Freecom.
EyeTV's a really nice application, and the Freecom's quite a nice receiver, although the bundled aerial is pretty poor. Also, it's digital-only, so you'd have to live somewhere that DVB is available. Nice & cheap at £31 though!