Vulnerabilities and exploits:
PacketStorm Security
SecurityFocus
bugtraq, vuln-dev mailing lists
lists exploits in vulnerability database
ImmunitySec
Info on several vulnerabilities in SPIKE distribution
CVE Database
CVE Search Engine
Full-disclosure mailing list
John R.
Words
Foundry Documentation
SNMP MIBs
Windows tools
NT Security
Samba Stuff
Linux tools
Assembly Language Debugger (ALD)
Despotic Unix Debugging Engine (DUDE)
HTE hex editor/disassembler