There are a number of great hacking and security websites on the web. Some of them are more interested in hacks, such as, and others are more interested in security–whether defensive or of a more offensive nature. Here, are some that are particularly useful and interesting:

2600, the Hacker Quarterly (see review)
AntiOnline, a community of security, network and computer professionals
Cult of the Dead Cow, creators of BackOrifice
Google Hacks
Google Hack Honeypot
Hack In the Box
Hack This Site, a free, safe and legal training ground for hackers to test and expand their hacking skills., developers of nmap, a free open source utility for network exploration or security auditing. Lifehacker, The Productivity and Software Guide .
Make:, a hack anything 'zine, run by O'Reilly. (see review), all the tools needed for wardriving