Odds are you have probably run across Wikipedia (http://www.wikipedia.org/) already, but if you have not, jump on the bandwagon.

Wikipedia is a completely user maintained (aka Web 2.0) website where the community updates and adds new information. You can find virtually anything from historical events to old TV series on the site in, usually, great detail. A lot of applications (such as music libraries) now connect to Wikipedia to pull information about the content users are currently accessing.

Be sure to add Wikipedia to your bookmark list and contribute to continue to make the site grow!