- FireGestures - Allows you to use mouse gestures to control aspects of Firefox, like navigating back and forth through pages, etc.
- Digg Firefox Extension - Provides insight into how many "diggs" the current page has received on Digg.com, enables you to submit the page to Digg.com, and shows you mini-views of the most "dugg" stories at the moment.
- IE View - An oldie but goodie, allows you to immediately open the current page in Internet Explorer, for when people have unfortunately written their pages in a way that they do not render correctly in Firefox (happens with a lot of Intranet pages written with Front Page, for example).
- Interclue - Is this plug-in absolutely necessary? No. It is cool and fun to see previews and statistics of pages before you even go there? You bet. :-)
- ScribeFire - A blog editor that integrates with most blogging sites and allows you to post directly to your blog from your browser, in some cases with better rich text editing and image and video sharing than you will get from the RTE that is provided online by your blogging platform. (Note: if someone can point me to a free, more full-featured [multi-indent lists, table support, etc.], whether it's a browser plug-in or not, I'm open to suggestions)
- Shareaholic - A tool that allows you to share a page or link using almost any of the available social bookmarking tools out there (delicious, digg, facebook, stumbleupon, twitter, etc.).
- Tab Catalog - Renders the contents of all open tags as navigable thumbnails.
- Web Developer - Still one of the most useful add-ons out there for Web developers. It provides insight into styles applied (and real-time editing of them), images embedded, cookies downloaded, and more features than I could possibly do justice for Web site and application developers.
Are there alternatives to the above that you think do a better job?
Are there add-ons that you use on a day-to-day basis that you think are also worth consideration?
A great list of add-ons for Web developers and Internet socialites can be found here.
My favorite add-ons from this bunch so far are the FireShot (for immediately creating, annotating and saving as JPGs screenshots within Firefox) and PicLens (for visualizing as 3D walls images from Google Images, Amazon, and News Media outlets).