Just Math Tutorials is a great FREE site created to help students with math.  Patrick does a great job at explain some very tricky math concepts.  As I looked through this site I felt it would fit with middle to high school students best.  However the Misc and Arithmetic sections could be used with upperelementary class as well.  Patrick JMT Math Video Tutorials has a YouTube Channel with most of these videos.

The video embedded below shows how to convert decimals into fractions.