You can ask your friendly hackers on this site to scan any site you care to name for you... and they'll do it while you wait! To experience this in the comfort of your own home check out the The Infinity Project

A perl module to craft custom ethernet packets. Nice! I've created a bare-bones Arrowpoint load-balancer keep-alive simulator for testing some proprietary software using it. Very very useful... You can find it here: Net::RawIP Home Page

How much can any web server that you visit find out about you without much trouble? Look here to do an automatic test.

How about a database of "all publicly known vulnerabilities and security exposures"?

Yesterday I founded a Yahoo club for the discussion of Samhain.

The Samhain filesystem integrity monitoring tool http://samhain.netpedia.net/ is a vast improvement over tripwire and the like. It offers a steganographic option to hide your datafiles and log files, making its presence hard to detect and meaningfully modify. It can also report to a central log server to avoid leaving obvious traces through syslog, or cleartext email.