My favorite site lately (and into the foreseeable future) is Wikipedia, a continually evolving community-written encyclopedia: http://www.wikipedia.org/ Why I like it: Philosophical reasons: GNU Free Documentation License, Open, etc… You can get lost for hours. (all inter-linked) I keep learning really interesting/useful things. I can correct people's writing. ☺ Try it out and try not to get addicted. I dare you.