Convert any video to MPEG-4

Handbrake is an open-source utility for converting video from any source into MPEG-4 files; it's especially useful if you want to rip movies and TV shows from your DVDs and watch them on your Mac. Handbrake comes with a ton of built-in settings, so you can also easily convert DVDs specifically to watch on your iPhone, iPod, or even AppleTV, PS3, or PSP. You get a lot of options for controlling framerate, codecs, audio handling (including support for multiple sound tracks), and even nuanced settings for B-Frames, CABAC coding, and the like--but Handbrake's chief quality is its ease of use, so less finicky users can usually convert DVDs with just a single click.

As with many free applications, your mileage may vary depending on your setup and what you're trying to accomplish (for example, Handbrake can be very slow on older machines, and it can also have trouble with DVDs made using camcorders and other apps). Also, there isn't much handholding when it comes to support, although at least stability has improved in recent versions. Fortunately, though, Handbrake is popular and you can often find answers to almost any technical question in the developer's active forums.