Native you tube client for several platforms;
http://flavio.tordini.org/minitube (http://flavio.tordini.org/minitube)
I use this on Linux and like it a lot. It's free on Linux ( although the guy accepts donations), costs 8.99 UK pounds for Windows.
A screenshot;
(http://img580.imageshack.us/img580/184/minitube007.png) (http://img580.imageshack.us/i/minitube007.png/)