Stage'D is definitely a work-in-progress, but already there's lots of fun to be had. You can pick characters and choose costumes for them. Then you can pick from a library of animations for them to perform, and don't forget to give'em some dialog! Pick some scenery and you officially have a comic, easy as that.
RefSeek's guide to the 25 best online resources for finding free educational videos. With the exception of BrainPOP and Cosmeo, all listed sites offer their extensive video libraries for free and without registration.