Billed as the web’s most extensive mathematical resource, provided as a free service to the world’s mathematics and internet communities as part of a commitment to education and educational outreach by Wolfram Research, makers of Mathematica.
A free rapidly growing site with videos on a wide range of academic topics, exercises (mostly math for now) and extensive tracking software. Khan Academy is one of our favorite sites and has been getting a great deal of positive press and funding.
Created by the University of Warwick in the UK, IGGY is a social network designed to help gifted young people between the ages of 13-18 realise their full potential. It gives members access to great educational resources and encourages them to work with top academics and other gifted young people around the world.