This blog comes from two public elementary teachers. It's full of free resources for math and language arts learning. You can download pdf's and powerpoint files including games, learning centers, worksheets and more. It may take a bit of searching if you're looking for something specific, and I found the amount of ads pretty distracting. But there are hundreds of quality, free resources here.
Online, interactive program for learning music reading and theory.
This non-profit organization offers over 100 free self-paced, online, college level courses.
This online math program is designed to help students with math problems (including dyscalculia.)
This hands-on grammar curriculum includes CD ROMs, teacher manuals, and games for learning gramma
Online, super-hero themed science games for elementary and middle school levels.
This program includes videos, worksheets and quizzes for history learning in jr.