Exploit Software

Exploit World
Archive of exploits for many systems. Pages have not been updated since 1998 and are preserved only for posterity.
http://www.insecure.org/sploits.html

John the Ripper password cracker
A portable password cracker with built-in efficient implementations of multiple password hashing algorithms found on various Unix flavors. Additionally supports Kerberos AFS and Windows NT LanMan hashes, plus many more with contributed patches. Officially supported are most Unix-like systems (including Mac OS X), Win32, DOS. There're unofficial packages for BeOS and OpenVMS.
http://www.openwall.com/john/

Rscan
Tool that lets a system administrator run complex or simple scanner scripts on any number of machines in a heterogeneous environment. Unmaintained since 1995.
http://www.protomatter.com/rscan/

Vapid Labs
Lists vulnerabilities, white papers and utilities.
http://vapid.dhs.org/