Some of them are fairly common, others a little geeky and for specific uses.

These are however the plugins I use or have remained installed on Firefox for an extended period of time, and many might prove useful.

Pick up the collection here:- Blogger SEO & Internet Marketing Tools

Individual plugins

1. SEO Link Analysis - Adds essential data to Google Webmaster Tools & Yahoo! Site Explorer
2. StomperTools - A totally unique plugin – this is why the Stompernet guys rock
3. TableTools - Ever wanted to reverse the sorting of an HTML table – this can do it, though you might need to create an extra column with a reverse index.
4. User Agent Switcher - Prowl around the web as Googlebot and interesting things can happen
5. Amazon S3 Firefox Organizer(S3Fox) - The easiest way to add files to Amazon S3 for casual users.
6. Talon: Screen Capture & Aviary.com Quick Launch – Look on this one as a bonus as it was just added, might prove to be a total Snagit replacement for those times I just need to grab part of a page.
7. Extended Copy Menu - Makes it easier to copy/paste HTML rather than text
8. Save Complete - Save complete webpages correctly for later reference – especially good for things like complete sales pages
9. Better Google Analytics (BetterGA) - Enhances Google Analytics with a compilation of user scripts.
10. XPath Checker - One of 2 applications that allow me to try to learn Xpath – useful when playing with scraping ;)
11. XPather - One of 2 applications that allow me to try to learn Xpath – useful when playing with scraping ;)
12. CacheViewer - This is an extra – for those times when you just know you saw a great picture, and can’t remember, or for finding videos ;)
13. Screengrab - My favorite of all screen grabbing software – uses the Mozilla engine to render a full page extremely fast, then you can go back at a later date to edit. Also own commercial Snagit, but this gets used more often.
14. Roboform Toolbar for Firefox - Don’t remember passwords, they just clog up your head
15. IE Tab – Essential for people who don’t want to load IE… ever
16. Evernote Web Clipper - Saving complete pages for future reference – I am starting to use this more and more, planning for future blog posts and major projects
17. PDF Download - I download PDFs a lot, and it is annoying when you click a link and discover it is a PDF, and it tries to load in the browser – the view as HTML option doesn’t always work very well
18. KGen - Steal other people’s primary keywords
19. iMacros for Firefox - For when you want to automate things like submissions of articles, videos, social bookmarking etc
20. Google Global - I use this to check US/UK search results with personalized search off – especially useful when posting search results in a blog post and you want the reader to see roughly the same results as you do.
21. YSlow - How fast is your website, and how to fix it
22. Greasemonkey - Need to add lots of cool plugins, found on Userscripts site – I will add an update to this post including essential Greasemonkey scripts at a later date
23. Web Developer - My default tool for working out what is happening or going wrong with CSS
24. Firebug - The primary reason to add this is to use Yslow and Google’s Page Speed plugins, though currently I can’t find Page Speed listed – otherwise I really don’t need both this and Web Developer
25. Live HTTP Headers - For checking redirects, snagging cloaked affiliate IDs etc. Also great to find the location of videos supposedly being cloaked from Amazon S3 for download.
26. FoxyProxy – For people who want to be a little anonymous, or when for some reason you can’t access a site as you
27. SearchStatus - Can load in the status bar rather than as a full toolbar, thus I have this on all the time without consuming screen real estate
28. Power Twitter - Can slow loading a bit, but makes the Twitter experience totally different
29. ScribeFire Blog Editor - I tend to use the WordPress interface more, due to lots of custom fields for SEO that need to be filled out – would be great if this somehow could work with Headspace.
30. Shareaholic for Firefox - If you really must use lots of social bookmarking sites
31. Delicious Bookmarks - For public bookmark sharing
32. StumbleUpon - Don’t forget to follow my stumbles on Stumpleupon http://andybeard.stumbleupon.com

Not In Collection (Not on Mozilla)

SEO For Firefox – for data when you need it

SEO Toolbar – for data while you surf

Free Download Manager – I have tried lots of others, but this is my download manager of choice, mainly because it remains free, is now open source, and has never had a corrupted database (a major factor)

Google Page Speed – New addition from Google to check out the speed of your web pages – strangely the thing which slows my blog down the most is their own Google Friend Connect bar at the bottom of the page.