Since 2004, makers of high definition cable boxes have been required to include a FireWire port to allow consumers to record television in a digital format. So Andy Ihnatko's pick from MacBreak Weekly 398 is a free application that makes use of this little known feature: FireRecord Desktop DVR. All you need to record TV in full HD is this app, a FireWire cable, and a Thunderbolt adapter (if you're using a newer Mac).
FireRecord will capture any unprotected channel digitally, without having to convert from analog first. It produces an MP2 file, which you could either play back using VLC, or convert to a modern format such as MP4. All broadcast TV channels will work with this, and you may find that some cable channels will work as well.
FireRecord can even control your cable box, so it can turn it on and change the channel to record something at a scheduled time. It also can be programmed for recurring events. FireRecord will even work with shows that you play back on a DVR.
To hear more FireRecord Desktop DVR, check out MacBreak Weekly episode 398 with Leo Laporte, Andy Ihnatko, and Rene Ritchie.