Music Theory Online

http://www.musictheory.net/index.html

Ricci Adams' Musictheory.net

This is a great site that teaches you all aspects of musical theory in a series of Flash-based lessons. Learn about notes, clefs, scales and much more. The web site and all exercises and lessons are created by Ricci Adams.

Ricci Adams first envisioned Musictheory.net during his senior year of high school. Soon afterwards, he created his first lesson: The Staff, Clefs, and Ledger Lines. The Interval Ear Trainer was developed a few weeks later and the site officially launched on January 1, 2000. Since that date, he has authored over thirty new lessons and several new trainers.

Poissonrouge.com - Games For Children

http://www.poissonrouge.com/

Poisson Rouge is an amazing site. It contains lots of free fun and educational games and activities for children (approx. 3-7 years old). It is also beautifully designed, and completely ad free! Highly recommended!

The activities include an alphabet games with very nice animations (one in French and one in English), a coloring game where you learn color mixing, a game to learn numbers 1-9, puzzles, toys (including a pretty caleidoscope), and a piano to learn music. This is my all-time favorite website for kids!

If you like Poisson Rouge, you should also have a look at the similar website Boohbah.tv.

Starfall.com - Online ABC Exercises

http://www.starfall.com/

Starfall.com is a free on-line service that helps children learn to read. It includes lots of ABC animations, animated interactive books and other reading exercises. There are also lots of downloadable materials such as handouts for classroom use. Perfect for home schooling. The site is completely ad-free. 

Free Algebra tutorials

http://www.algebasics.com/

Free Video Tutorials for basic Algebra.