SeaMonkey Extensions compatible with version 2.2 for any regular user. If you are missing any, then it is not compatible. Of course, this is not exhaustive list, so visit frequently for any inclusion.
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).
An extension that adds direct links to download YouTube videos as MP4 and FLV. It has a simple interface and it downloads videos directly from YouTube. The extension integrates with YouTube's interface and adds a download button below the player.
The first and only download manager/accelerator built inside Firefox!
Protect your privacy. See who's tracking your web browsing and block them with Ghostery.
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.
Download all the links, movies and audio clips of a page at the maximum speed with a single click, using the most popular, lightweight and reliable external download managers.
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.
Find out which websites you can trust. WOT adds intuitive traffic light-style icons next to search results and URLs to help you make informed decisions about whether to visit a site or not.
Fight the text ads! Element Hiding Helper is a companion extension for Adblock Plus meant to make creating element hiding rules easier.
With EPUBReader you can read ePub files just in Firefox. No additional software needed!
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...
FireShot Webpage Screenshots captures pages entirely. Demo: http://bit.ly/RlBQMV
Screenshots can be quickly captured and:
― Saved as Image or PDF
― Sent to clipboard
― Annotated *
― Uploaded *
― E-Mailed *
* OS Windows only
The quickest way to find out if your computer is infected!
Bitdefender QuickScan is a very fast antivirus scanner, able to determine in a matter of seconds if a system is infected with malware.
More on http://quickscan.bitdefender.com/faq