Here are some useful resources:

YouTube has great educational videos. A few series that I like to use are Math Antics, Anywhere Math and Mashup Math. Just go to YouTube, search the series and the topic. For instance: Math Antics Proportions.

This document has links (in English and Spanish) to a whole suite of videos for Math 6:
Video Links for Math 6

Other useful websites: (Select Reagan Middle School and the password is rwreaganms) (great site, but not free)

These sites have practice problem worksheets with answer keys:

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