Lifehacker might be my favorite website, because they're probably one of the best education websites out there without even trying. For example, they've found another great vocabulary study resource called VerbaLearn. It's perfect for students (or maybe you) who are getting ready for the SAT, ACT or GRE. One great feature is being able to create podcasts of vocabulary for iStudying, but the best part has to be the smart vocabulary lists that remove words once you've demonstrated mastery (so you can focus on the ones you don't).
A few months ago, Lifehacker wrote about Teach2000, a free flash card creating program that I imagined could help build a great lesson on how to study. Combine them with FreeRice, the addictive vocabulary game that raises money for charity, and you have the beginnings of a pretty good unit on study skills.