Fyodor is running a nice list of security tools at http://www.insecure.org/tools.html, even
if not included in the list, Nmap is one of the most used and useful
security tools available.
Smokeping, http://oss.oetiker.ch/smokeping is a great tool written by Tobias Oetiker and Niko Tyni. They have many probes available, dig, NET:DNS, fping, echoping, curl, etc., but no probe written for hping! I'm not a perl programmer, but would love to see an hping probe for smokeping.