Multi Topic Sites
Spark Notes.com
Many topics covered

Teaching Learning On The Web
Almost 900 Topics

World Lecture Hall
Hundreds of Topics aimed at University Students - but many free Lectures etc

agabaga
About how life works
Some FREE Lectures

Anthropology Tutorials

Bible Studies Resources

Fizzics Fizzle - Physics

Free English

Ref Desk
A huge list of topics to look things up.
If not here try Caithness.org Reference Section
Growing list of encyclopedias and Sites on Many subjects.  Or try the Links Section topics

Computing
Dell Free Computing Classes

Inform IT

Resource Guide in Computing Software

Sports
Online Judo Lessons

Swim Workouts