Here is a list of useful Firefox extensions for web developers and programmers.
1. Greasemonkey
Greasemonkey allows users to install scripts that make on-the-fly changes to specific web pages. Greasemonkey can be used for adding new functionality to web pages, fixing rendering bugs, combining data from multiple webpages, and numerous other purposes.
2. Firebug
With Firebug you can [...]

Tired of installing plugins and themes by opening FTP and uploading or you are unable to use FTP in office, then this extension is for you. OneClick Installer for Wordpress Firefox Extension makes it easy for you to upload plugins and themes in a single click without opening FTP program.
Anirudh made this extension, he [...]

I have been playing with a Firefox extension called ThumbStrips, this is a quite nice tool it makes screenshots of the sites you visit.
ThumbStrips makes a filmstrip of thumbnails of the web pages you visit, so that you can go back to them and see what you browsed. In other words this extension makes [...]

Smart Toobar is a Firefox add-on which enables you to check Google page rank and alexa rank of a website. This toolbar is not an official product of Alexa, it is a product Smart Pagerank.
Using smart toolbar you can

See the Alexa Rank of every page you visit.
See the Google PageRank of every page you [...]

PicLens is a Firefox extension that allows you to launch full screen slideshows while browsing photos.
With piclens installed you can full-screen slideshows while browsing Google or Yahoo images or Flickr. Piclens works with sites that support media RSS. The image you clicked on opens in full screen with thumbnails for other images on the [...]

BlueOrganizer is a firefox add-on from AdaptiveBlue, which allows you browse the web faster and smarter in just a single click. It helps you organize your life online, it understands what is in a page like books, movies, restaurants, etc and then links them to the online tools to make browsing easier.
For example you [...]