Rich's Tongfamily (Richtong.net add-on)

Nessus. Supposedly one of thge best port scanners. I just love Languard and how easy it is to use. Particularly for SMB vulnerabilities.

scanner comparison

Network Computing | Feature | Security | Vulnerability Assessment Scanners | Page 1 | January 8, 2001

GIAC: Global Information Assurance Certification – Home Page Seems to be a good site to look at for how certification works on security.

eEye Digital Security. Best scanning tool is now on Windows

Sysinternals Freeware – Utilities for Windows NT and Windows 2000. A very nice set of utilities for Windows

Security Tools : ScannerAn easy place to fine the scanner stuff. Watch out for viruses in them though!

NetworkEval.COM Home PageAnother site with something that identifies all shares

SC Magazine. Of course there is a security trade publication!

Nmap — Free Stealth Port Scanner For Network Exploration & Security Audits. Runs on Linux/Windows/UNIX/Solaris/FreeBSD/OpenBSD. This appears to be the port scanner of choice.