Take a stroll through the great ocean of applications for the beloved Mozilla Seamonquey, icon by victor1410, deviantart.com
Blocks annoying video ads on YouTube, Facebook ads, banners and much more.
Adblock Plus blocks all annoying ads, and supports websites by not blocking unobtrusive ads by default (configurable).
The first and only download manager/accelerator built inside Firefox!
The best security you can get in a web browser!
Allow active content to run only from sites you trust, and protect yourself against XSS and Clickjacking attacks.
Organize your schedule and life's important events in a calendar that's fully integrated with your Thunderbird email. Manage multiple calendars, create your daily to do list, invite friends to events, and subscribe to public calendars.
Restyle the web with Stylish, a user styles manager. Stylish lets you easily install themes and skins for Google, Facebook, YouTube, Orkut, and many, many other sites. You can even customize Firefox and other programs themselves.
The Web Developer extension adds various web developer tools to the browser.
FoxyProxy is an advanced proxy management tool that completely replaces Firefox's limited proxying capabilities. For a simpler tool and less advanced configuration options, please use FoxyProxy Basic.
Displays a country flag depicting the location of the current website's server and provides a multitude of tools such as site safety checks, whois, translation, similar sites, validation, URL shortening, and more...
With EPUBReader you can read ePub files just in Firefox. No additional software needed!
United States English Spellchecker for Firefox, Thunderbird and SeaMonkey by Kevin Atkinson and Geoff Kuenning.
To enable, right-click in a multi-line text box, select "Languages", then "English (United States)".
AutoPager automatically loads next pages when you reach the end of a page. It works on a ton of sites,Google,Yahoo..
It works well with most other add-ons adblock plus, WOT and most of the greasemonkey scripts.
You can also try AutoPagerLite.
— Open web pages saved with Internet Explorer or other browsers (MHT)
— Save many tabs, video and audio reliably, in a single ZIP file (MAFF)
— Return to the original site you saved a page from, and more!
Professional Geo Add-on with security features and advanced network tools. Anti-phishing. Protection against DNS spoofing and fake sites. All DNS records for domain. The real location of web server, country flag, extended information about datacenter
ReminderFox displays and manages lists of reminders and ToDo's. ReminderFox makes sure you remember all of your important dates via easy-to-use lists, alerts, and alarms, right in your browser without the need for a separate calendar program.