This website is one that I can really get behind as it offers something worthwhile for nothing and it is still legitimate. It is the Khan Academy and it was founded by Sal Khan after he found the maths tutoring videos he posted on youtube to help his cousins in other cities were well received by more people than he expected. A need was revealed and during the 2011 TED conference Khan Academy got recognition and has continued to grow from there.
Videos are posted by staff and volunteers. The range of subjects is seemingly endless and the site even tracks your progress. The academy has even put a game-like spin on learning by offering various badges to mark milestones.
This is a very worthy recipient of my website of the week (and possibly the year) as this not-for-profit offers a way to learn new things or brush up on old skills without the waiting or finding someone to help.