QuickTime Player from Apple allows the playback of quicktime movies (.mov) and many other formats:

The new QuickTime Player not only delivers startling quality, but it's easier to use than ever. It requires no set up for content that streams over the network. Instead, QuickTime Player automatically determines your system's connection speed and chooses the highest quality stream for the amount of bandwidth you have available. And if you ever lose a connection while watching streaming video, QuickTime Player automatically reconnects. Now, thats convenience.

* Playback of 3GPP and 3GPP2 files
* Playback of MPEG-4 video, H.274, AAC audio & Instant-On media
* Easy-to-use controls
* Enhanced interface
* Bass and treble controls
* Balance control
* Streaming media support
* Ability to save movie favorites
* Ability to view VR & interactive content

Changelog:
QuickTime 7.6 includes changes that increase reliability, improve compatibility and enhance security. This release is recommended for all QuickTime 7 users.

What’s in this update?

Video:
Improves single-pass H.264 encoding quality
Increases the playback reliability of Motion JPEG media

Audio:
Improves AAC encoding fidelity
Audio tracks from MPEG video files now export consistently

Application Support:
Improves compatibility with iChat and Photo Booth

Security:
For information on the security content of this update, please visit this website:
http://support.apple.com/kb/HT1222