Mostly just to watch, the ones on Youtube aren’t very entertaining.

Both AnimateClay.com and StopMotionAnimation.com are useful sites to get tips, tricks, tutorials and help with stop motion (which includes claymation). Both sites also have forums where both amateurs and pros hang out and people can answer and ask all sorts of questions there.

http://www.stopmotionanimation.com/handbook/

http://www.animateclay.com/index.php?name=Sections&req=listarticles&secid=3

Here are some online resources about the basic principles of animation. These principles can and should be applied to any genre or medium you choose to work in, whether that be drawn, CGI, or stop motion animation.

http://www.idleworm.com/how/index.shtml
http://www.awn.com/tooninstitute/lessonplan/lesson.htm
http://www.animationarena.com/principles-of-animation.html
http://www.animationmeat.com/notes/notes.html

Finding good stop motion films on Youtube can be difficult because you need to wade through people’s amateur videos, most of which aren’t very good. But to be fair, everyone needs to start somewhere and the entire stop motion community, both animators and enthusiasts alike, should be thankful that there are still people interested enough in stop motion to give it a try.

To find good movies on youtube, you just need to know what you’re looking for in advance. I could give you the names of some good stop motion films and shorts.