MS-MPEG4v2 for Mac OS X
screenshot of codec in action
Download Codec (440KB)
Links:
DivX Doctor II - Needed for reliable audio playback.
FFmpeg - They made the decoder.
DivOSX - They made 99.9% of Quicktime interface.
Microsoft - They made the codec.
Digital Archive Project - They've got some nice content!
Henry Mason - That's me.