If you are paranoid about people ARP spoofing or flooding on your network you can use ARPWatch-NG, ARPWatch-NG is a continue of the popular original ARPWatch from ftp://ftp.ee.lbl.gov/.
ARPWatch monitors MAC adresses on your network and writes them into a file, last know timestamp and change notification is included.

It can be used it to monitor for [...]

It’s good to see work on open source tools in the countermeasure department aswell as the attack and penetration arena.
It’s a shame since Snort and Nessus have gone semi-commercial.

I hope more people invest their time in good IDS, Firewall and IPS systems, I love things like IPCop and hope to see more products like HLBR.
HLBR [...]

I remember some time back Netcraft developed an anti-phishing toolbar for Internet Explorer Exploder and Firefox.
You can check it out here:
Netcraft Toolbar

Protect your savings from Phishing attacks.
See the hosting location and Risk Rating of every site you visit.
Help defend the Internet community from fraudsters.

Then recently Google has come out with the Safe Browsing Extension for [...]

1. BackTrack
The newest contender on the block of course is BackTrack, which we have spoken about previously. An innovative merge between WHax and Auditor (WHax formely WHoppix).
BackTrack is the result of the merging of two Innovative Penetration Testing live Linux distributions Whax and Auditor, combining the best features from both distributions, and paying special attention [...]