I know a few vidders who put their work up on Vimeo (I think you can also password protect it there).

I haven't had personal experience with Youtube copyright, but I did find a couple of posts that might be helpful:

http://transformativeworks.org/news/youtube-blocking-your-vids-exercise-your-right-fair-use

http://transformativeworks.org/mixed-messages-youtube’s-copyright-school

http://www.delicious.com/metafandom/vidding+fair_use