Well, in my new job as in IT Security Researcher, I have to read a large number of cracking related pages. Here's some of the ones I check the most frequently.

Nmap, security scanner

Stuff I have here
Just general stuff on cracking/hacking. Things you can get information on about on the web, such as security and encryption. Also pages full of really handy software and libraries. Mainly for linux, but some for NT.