I discovered a great list of the top 100 network security tools voted by 3243 users of the nmap-hackers mailing list. Every tool mentioned has a description, a homepage link to the developer website, icons that tell you if it works on your system and if it costs money. All utilities belong to a category, you have the option to display every category (like vulnerability scanners).
Top ten tools are Nessus, Wireshark (former Ethereal), Snort, Netcat, Metasploit Framework, Hping2, Kismet, TcpDump, Cain and Abel and finally John the Ripper. This is a great collection of the most important network security tools of 2006.
Update: It has been six years since the initial article has been published on the site. Good news is, it has been updated throughout those years so that it is still very useful even today.
Some old programs that are no longer maintained have been removed from the listing, and new programs have been added to it. The top 10 has changed quite a bit, and looks like this as May 2012:
- Cain and Abel
- John the Ripper
You will notice that the ranking has changed, and that new programs have made their way into the top 10, while others have dropped from it. The site authors are constantly updating the list with version and release information, which makes it really easy to find programs that are still in active development, and avoid others that have not been in active development for a long time,
Each tool links to the project homepage, a Wikipeda entry (if available), and compatibility and cost information that you may find useful as well when making your selection. You can still use the categories in the sidebar to only display tools that serve a specific purpose.