https://en.bitcoin.it/wiki/Main_Page
or simply
http://en.wikipedia.org/wiki/Bitcoin
bitcointalk.org / Under a large scale attack and down at the moment.
http://www.reddit.com/r/Bitcoin/comm...attack_change/
Like madtwin said, it might be better to learn about crypto coins with one of the countless alt coins. There are a lot of them with rather low difficulty so even solo mining without special hardware is possible. At the moment even the less popular have a surprising high $ value.
One of the more popular alts:
http://feathercoin.com/
Some alt boards:
https://cryptocointalk.com/
http://www.altcointalk.co.uk/
.