TabletMath is actually a subscription service, but they put over 250 math videos on YouTube for homeschoolers, including videos that correlate with popular homeschooling math programs Saxon and Math-U-See.
http://www.youtube.com/user/tabletclass/videos
These are similar to Khan Academy in some ways, but more visually appealing.
Some of the videos correlate with a free math quizzes site: http://homeschoolmathquiz.com/
