After opening the movie you want to rotate in Quicktime, go to Window/Show Movie Properties (or better press cmd-J shortcut).
Select the Video Track and using the rotate buttons on the bottom, you will be able to rotate and flip the movie!
So simple… Without the need of any third $oftware..
Apple MAC just WORKS !! 
Only available if you buy quicktime pro. For features that should come as standard as part of the OS Apple Mac just COSTS.
I have not bought any quicktime pro, and rotate works. I think it comes in PRO version, already with Leopard and MAC OS X since it was installed on my new iMac already (the quicktime pro version)
I have MAC OS X and I only have the quicktime viewer. The Show Movie Properties is only available on pro version.
I have Quicktime Player Version 7.6 (472) which already installed on Mac OS X 10.5 when I bought my iMac. You should check more carefully, the “SHOW MOVIE PROPERTIES” is there, under the Window menu
You may also use iDealshare VideoGo to Rotate QuickTime MOV files without reencoding
It also can rotate iPhone video, MP4, DV, AVI, WMV, MKV, MPG, AVCHD etc.
It can rotate video 90 degree, 180 degree, 270 degree and etc.