Video Video Programs
DivX
DivX
Version: 6.0.0 Date: Dec 7, 2005
Description: This codec (for QuickTime) handles the DivX video format (which is an MPEG-4 based format).
DivX
DivX Converter
Version: 1.0.0 Date: Dec 7, 2005
Description: (untested)
D-Vision
D-Vision
Version: 3.1.5 Date: Sep 1, 2005
Description: This is a GUI front-end to the open-source, command-line mencoder tool for ripping DVDs and encoding video files. D-Vision's GUI is a nice way to select all the commands needed to make mencoder work. One very nice feature is the auto-cropping tool! Also, I think you can convert the audio tracks of a DVD to a user-friendly format like MP3, saving the 2-step approach of using MacTheRipper and mAC3dec!
DVDibbler
DVDibbler
Version: 1.8.4 Date: Aug 25, 2003
Description: This is another GUI front-end to the open-source, command-line mencoder tool for ripping and converting DVDs. I prefer D-Vision over this ripper/converter. Under Panther, I had lots of problems with this app, and under Tiger it just doesn't work (for me).
ffmpegX
ffmpegX
Version: 0.0.9x Date: Sep 28, 2006
Description: This is yet another GUI front-end to the open-source, command-line mencoder tool for ripping and converting DVDs. For DVDs, D-Vision and Handbrake are easier to use, but ffmpegX offers a lot more options and can easily convert exists files from one format to another.
Handbrake
Handbrake
Version: 0.9.1 Date: Oct 8, 2007
Description: Handbrake is a nice, all-in-one DVD ripper and converter with some very nice cropping features. It was even able to rip stuff that D-Vision couldn't. In general, D-Vision and DVDibbler provide more features than Handbrake, but if you just want simple ripping and converting, try Handbrake. On my Mac, though, Handbrake is 2-3 times slower than D-Vision.
Forty-Two
Forty-Two
Version: 1.6.2 Date: Jul 19, 2003
Description: Forty-Two is another free DVD ripper and converter. It supports some formats that some of the other rippers/converters, but I couldn't get all of them to work. Try Handbrake, D-Vision, or DVDibbler instead.
MacTheRipper
MacTheRipper
Version: 2.6.6 Date: Mar 10, 2005
Description: A great DVD ripper. It doesn't have all the features of some Windows rippers (like DVD Decrypter or DVD Shrink), but it does the job. MacTheRipper also has the wonderful capability of extracting the audio tracks from a DVD. These will usually be in the AC3 format, so use mAC3dec to convert to a user-friendly format.

Looks like the official MacTheRipper website has been taken down.

mplayer
Mplayer OS X
Version: 2.0b9r5 Date: May 20, 2005
Description: Mac port of the legendary mplayer.
Perian
Perian
Version: 0.5 Date: Sep 29, 2006
Description: Advertised as the "the swiss-army knife for QuickTime", Perian's QuickTime plugin is supposed to play just about every video format, obsoleting the stand-alone codecs for DivX, XviD, etc.
QuickTime
QuickTime
Version: 7.5.5 Date: Sep 8, 2008
Description: An absolutely essential tool for the Mac!
RealPlayer
RealPlayer
Version: 10.0.0 build 352 Date: Feb 7, 2006
Description: An essential tool. Plays RealAudio and RealVideo files and streams.
SimpleImage
SimpleImage
Version: 4.0 beta 5 Date: Jan 30, 2004
Description: A good image/movie viewer and slideshow tool.
vlc
vlc
Version: 0.8.5-test3 Version: Apr 20, 2006
Description: Plays a variety of video and audio formats, including streaming files and ripped DVDs.
MediaPlayer
Windows Media Player
Version: 9.0 Date: Aug 17, 2003
Description: Plays a variety of video and audio formats.
XviD
XviD Codec
Version: 0.5.1 Date: Apr 6, 2005
Description: One guy has compiled a version of the XviD codec for Mac OS X, but try Perian first.
XviD
XviD Delegate
Version: 0.1 Date: Jul 4, 2003
Description: This QuickTime component doesn't actually play XviD files, but it delegates XivD files to the DivX codec, which can handle them (apparently because they're similar, MPEG-4 formats). Try Perian first, though.

If you're playing DivX/XviD video, you might also need to decode AC3 audio; the same guy (Adrian Bourke) who made this XviD Delegate also make a very handy AC3 component for QuickTime.

The information above represents my experience with a certain version of each piece of software. I have no vested interest in any of these programs, and only provide this info as a guide (your experience and preferences may vary greatly!).

The version number listed is the latest version I have tried. To download the latest version, click on the name or the icon of the program, which should take you to the program's homepage, or to a software archive site. You can also track new releases at MacUpdate and VersionTracker.