"PrimaryAccess is a suite of free online tools that allows students and teachers
to use primary source documents to complete meaningful and compelling learning
activities with digital movies, storyboards, rebus stories and other online
tools."
Tutor USA is a site that offers a variety of useful links for mathematics teachers and students. In addition to free worksheets and lesson plans, Tutor USA has built a nice collection of video tutorials. The videos in the collection come from sources like YouTube, Blip.tv, and TeacherTube. Some of the videos are quick how-to videos while others are longer lecture-style explanations of mathematics concepts.