Add-ons

DownThemAll! by Nils Maier, Federico Parodi, others

The first and only download manager/accelerator built inside Firefox!

FlashGot Mass Downloader by Giorgio Maone

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.

FireFTP by Mime Čuvalo

FireFTP is a free, secure, cross-platform FTP/SFTP client for Waterfox which provides easy and intuitive access to FTP/SFTP servers.

Check out my new project, FireSSH!

Element Hiding Helper for Adblock Plus by Felix Dahlke

Fight the text ads! Element Hiding Helper is a companion extension for Adblock Plus meant to make creating element hiding rules easier.

The Pirate Bay (SSL) by SSL Search Bar

The Pirate Bay is a popular BitTorrent index. This search bar add-on utilizes SSL to protect searches between You and The Pirate Bay.

Kickass.to torrent search by kickass.to

Kickass.to torrent search with real time auto-completion

AutoPager by Wind Li

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.

Eccellio Science - Search Engine by Info Eccellio

Eccellio Science is fully dedicated to students and researchers that want to obtain fresh results and are very focused on Science matters. Not just Wikipedia as it often happen, but accredited and specialized websites. Enjoy Eccellio Science!

Torrents Fast Search by Nicu

Torrents search addon lets you search a constantly updated collection of torrent sites at once. Torrents search is easy to customize enabling you to enhance your torrent finding experience. http://torrents.to

Scroogle (SSL) by SSL Search Bar

*** Update: Feb 22, 2012 ***
Unfortunately, Scroogle has shut down permanently. Between Google gimping them, and a sustained DDoS, they have decided to close for good.

Moving forward, you may with to consider using Startpage or DuckDuckGo.

Wowhead by gizod

Wowhead Search

NCIS... by riley_heart