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