This site has quite a few free math learning resources. There are interactive lessons, printable worksheets and a worksheet generator, a few simple flash-based games, some webquests on fun math topics, and more. It's a no-frills website, that's not terribly interesting visually, but there are plenty of useful tools to explore.
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.