TeacherTube http://www.teachertube.com

TeacherTube has been around for a while, although there has been some effort recently to give it a bit of a facelift. You can browse through resources (including photos, documents and audio) that other teachers have posted, and/or use it to post host your own videos.  There is a lot of teacher-submitted content, which is a strength. Overall, there is too much advertising for my liking, and despite a recent upgrade, the design still seems a little dated.

SchoolTube http://www.schooltube.com

SchoolTube has many of the features of TeacherTube (the one possible exception is that SchoolTube hosts videos only, rather than other types of files). The big advantage of SchoolTube is that there is far less advertising, a nicer design, and faster upload times.  It just seems to generally work better than TeacherTube.

Documentary Heaven http://documentaryheaven.com/

This is a great collection of documentaries from around the internet.  It isn't designed specifically for school use, so there is quite a bit here that falls into the "controversial" category, to say the least.  But there is also plenty of content appropriate for the classroom. 

SNAGFilms http://www.snagfilms.com

THIS PAGE IS AWESOME (For teens and adults, mostly) Lots of popular and current documentaries, including National Geographic, NOVA, and other stuff like Human Footprint and Super Size Me.  There are some ads, unfortunately, but you can embed them in blogs and wikis, and save your spot if you don't finish the film, which is pretty cool.  It offers streaming only, no downloading, so perhaps watching it in class is a bit of problem.  You can also buy most of the docs right from the site.

DotSub http://www.dotsub.com

DotSub is a pretty specific site.  It offers many different videos with subtitles in a variety of languages. Excellent resource for ESL teachers.

NeoK1 http://www.neok12.com

THIS IS A GREAT SITE! A massive collection of videos, lesson plans and educational games. All material is screened by teachers, and organized by topic so you can find what you need fast.

WatchKnow http://www.watchknow.com

ANOTHER STELLAR SITE.  Similar to neoK12 this site offers literally thousands of learning videos organized by subject area for easy browsing.

TeachersDomain http://www.teachersdomain.org

This Site offers many excellent videos, including great PBS stuff like Nature and Nova. One of the best things about this site is that many of the videos are available for download, not just streaming, which makes them very useful for the classroom.

http://schoolwaxtv.com/

This site is new-ish, so the collection is still growing. Seems like it has potential.

Due credit: I learned about many of these sites by reading the excellent resources @ http://freetech4teachers.com, and from the my ever-knowlegable colleague, Phil ( http://cagestech.pbworks.com ).