TubeTV is a freeware program for Mac OS X Tiger, Leopard, and above which enables you to search for and save YouTube and other flash based web videos in a format suitable for playback on your Apple TV, computer (iTunes or QuickTime Player), video capable iPod, iPhone, or other mobile phone.
Although TubeTV has been tested most extensively with YouTube, it will probably work on most other web sites which make use of flash video. Note that some sites have advertisements and pop up windows which make things trickier, so these sites may be problematic (you may end up with an advertisement instead of the actual content).
TubeTV has a built in browser which can be used for most video sites, but using the browser is optional. If you prefer, continue browsing with your favorite browser (Safari, OmniWeb, Camino, and FireFox are supported) and then use TubeTV to grab the video when ready. TubeTV can either copy the URL from your default browser and re-load the page, or using the Download From... menu option, it can attempt to directly download the video.
For full functionality, QuickTime version 7.2 or later and Perian 1.0 or later are required. Favorites (bookmarks) require Mac OS X 10.5 (Leopard) or higher.
Please consider donating if you find this software useful. Donations encourage future versions of TubeTV and help keep the author from starving. ;-)