Well, theres tons of sites out there, you can use google to find a lot of them.
Heres couple of good links
The New UGN Security
Archive (doesnt have a lot yet, still underconstruction sorta = ) ) http://archive.undergroundnews.com
The Old UGN Security
KBase has tons of things you can learn from, it also has couple of hacking manuals in there. http://www.undergroundnews.com/files/texts/best.htm
Zone-h has some really good txt files and tutorials on computer security located here: http://www.zone-h.com/en/download
Packet-Storm also has tons of txts files you can learn from http://packetstormsecurity.nl/
If your looking for a specific tool, just search it in Google.
This site has some OK tools http://www.astalavista.com/
Just use google = ) Those links should help you get started