Security Tools and Browser Extensions
This site has a huge list of Firefox Extensions (Add-Ons) that are security tools.
https://www.security-database.com/toolswatch/FireCAT-Firefox-Catalog-of,232.html
And then there’s always this great list of general tools.
Top 100 Network Security Tools
After the tremendously successful 2000 and 2003 security tools surveys, Insecure.Org is delighted to release this 2006 survey. I (Fyodor) asked users from the nmap-hackers mailing list to share their favorite tools, and 3,243 people responded. This allowed me to expand the list to 100 tools, and even subdivide them into categories. Anyone in the security field would be well advised to go over the list and investigate tools they are unfamiliar with. I discovered several powerful new tools this way. I also point newbies to this site whenever they write me saying “I don’t know where to start”.