https://browsercheck.qualys.com/
Qualys BrowserCheck will perform a security analysis of your browser and its plugins to identify any security issues.
https://www.eff.org/https-everywhere
HTTPS Everywhere is a Firefox extension produced as a collaboration between The Tor Project and the Electronic Frontier Foundation. It encrypts your communications with a number of major websites.
NOTE: Encryption can severely impact performance over high latency connections such as Satellite.
WOT is a site scoring system similar to SiteAdvisor. SiteAdvisor was great at first and had potential until McAfee got their hands on it. This appears to pick-up where SiteAdvisor started and add a few features.
This add-on blocks scripts from running in Firefox. When you visit a website that wants to run scripts, NoScript will display a warning at the bottom of the screen, and give you the opportunity to allow scripts to run on a temporary or permanent basis. Not allowing the scripts to run can severely impact the performance of many web pages.
Adblock Plus is an extension for Firefox, Thunderbird, and several other applications with the primary goal of removing advertisements. It works by comparing ads that are about to be displayed with a set of filters that describe undesirable advertising. When you install Adblock Plus, it sets up a subscription to a basic set of filters that will meet the needs of most users. Many additional sets of filters are available for your use.
– Main.FredPettis - 2010-12-01