HttpWatch : An HTTP Viewer and HTTP Sniffer for IE and Firefox
Nikto2 : Nikto is an Open Source (GPL) web server scanner which performs comprehensive tests against web servers for multiple items, including over 6500 potent...
Buildbot : Buildbot is an open-source framework for automating software build, test, and release processes.
OpenDNS : The safest, smartest, fastest and most reliable DNS on the planet.
Wireshark is the world's foremost network protocol analyzer. It lets you see what's happening on your network at a microscopic level. It is the de facto (and often de jure) standard across many industries and educational institutions.