Tutorial and Flashcard Sites
Brightstorm: A collection of video explanations of math and science concepts presented by teachers and professors skilled at taking that which is complex and breaking it down to provide clarity.
Khan Academy: Looking for a little extra guidance with understanding a concept, strategy, or equations? Khan Academy features a library of over 3,000 learning videos covering everything from math to physics to finance to history.
Udacity: Free online learning with such courses as: Intro to Physics and Intro to Statistics: Making Decisions Based on Data
Wolfram/Alpha: An answer engine whose answers are computed based on data, rather than linking to other web pages. It can answer specific questions such as "How old was Barack Obama in 1972?" and can also assist with math and science equations.
Flashcard and Fact-Learning/Playing/Testing Sties
Anki: A downloadable flashcard program that will re-test users at predetermined intervals based on comfort with the information.
Quizlet: A great substitute for flashcards, you can make your own sets—vocab & definitions, foreign words & their English translation, musicians & their compositions, artists & their paintings, etc. It will then generate digital flashcards (which you can print out or have the computer read aloud), memory games, and even practice tests. It will read and spell foreign words in the language you indicate. You can even share sets you create with friends. It'll change the way you study!