Covering topics in Nature, Technology and Culture
ClearlyExplained.com is a reference website that takes some of the best bits of wikipedia combined with occasional extra explanatory comments.
Much of the content is similar to wikipedia but is presented in a slightly more reader friendly way. Wikipedia can sometimes be a bit overwhelming at first glance. This site gives a clear overview of the topics in three broad categories: nature, technology and culture.
Here are a few starting points...