Macintosh Underground Forums
Large Macintosh security and underground topic discussion forum.

Psyon.org
A Web Board with various topics of discussion.

WhiteBBS
Board for programming and general OS security.

HFX International Forum
Discussion forum for topics surrounding the underground, technology and the like.

The Shared Foums
Forums of the four largest mac hacking sites. Your ultimate connection to the macintosh underground world.

X-Ploit Team Forum
Forum dedicated to hacking, cracking, phreaking and other issues.

HardPlex.com
A new up and coming Hacking & Security Forum.

The Forbidden Web Archive
Security and Development Forum with a Security Basics Forum and Vuln-Dev.

SecureRoot
One of the worlds longest established hacking forums, offering resources covering everything from cracking to phreaking.

Neon Underworld
Forums on hacking, phreaking, and social engineering.

HackingForums.com
Hacking and Security forum for advanced hackers.

TiVo Techies
Technical discussion forum on TiVo hardware, hacks and mods.

HackerLounge.com
Variety of topics and tutorials related to Hacking and Phreaking.

HackerThreads.org - Security Forum
Discussion forums with tutorials, Hacking programs and miscellanious threads.