Links
Rankk
A great challenge page where I learned very much about all this and was the motivator to create an own page.
Revolution Elite
sabretooths unique challenge page where you can learn much. Try it!
Halls of Valhalla
Valhalla is a place for sharing knowledge and ideas. Valhalla allows users to submit code, as well as science, technology, and engineering-oriented news and articles, and we also affiliate with other IT-related sites. We provide a biography and tags for each affiliate so users can easily find the content they are interested in. Valhalla also has an assortment of fun challenges intended to help users learn more about programming contepts, computer science, engineering, mathematics, and more.
WeChall
WeChall unites some challenge pages to have a general ranking. Take a look at it and sign up.
LOSTPEDIA
A great resource and help for some challenges. It has detailed information about almost everything interesting in LOST.
Check it out.