Those are add-ons that I use daily. I am also a web developer so you might find there some web tools also.
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).
Collector's Note Great plugin for blocking adds
The first and only download manager/accelerator built inside Firefox!
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
IE Tab - an extension from Taiwan, features: Embedding Internet Explorer in tabs of Mozilla/Firefox...
Adds links to convert and download Youtube, MyVideo, Clipfish, Sevenload, Dailymotion, MySpace videos as MP3 files. Visit our site: http://www.video2mp3.net for more information
This extension allows you to execute common commands using mouse gestures, rocker navigation, scroll wheel navigation and page...
Polish spell-check dictionary for Firefox, Thunderbird and SeaMonkey.
The original Gmail notifier for multiple accounts. Allows you to receive new mail notifications along with viewing account details including unread messages, saved drafts, spam messages, labels with new mail, space used, and new mail snippets.
Help make Firefox better. The Add-on Compatibility Reporter enables you to report if the Firefox add-ons that you're using are working properly.
Statusbar button to turn the proxy on and off with a single click.
Toggles dictionaries automatically or manually and displays the currently selected one
Combined with the ChromeToPhone application for Android, this extension allows to send urls, text and files from Firefox to your phone or tablet.
Collections are groups of related add-ons that anyone can create and share.Explore Collections