These are the Firefox extensions I found out to be the best so far:

  1. Fasterfox: it tweaks your Firefox settings, in some situations you really go faster with a good ADSL line. However, it defaults not activating the "Prefetch" function, really useful in some situations (paged results of the search engines for example). Note that Fasterfox breaks the HTML 1.1 compliance of the browser by forcing the web servers to push more data than they would have instead. Remember to change your half connections limit if you got Windows XP or Windows Vista.
  2. ScribeFire (aka Performancing): It’s a plugin that helps you write your blog, I use it myself and I like it. Saves automatically the blog article you are writing if you close the window, has many publishing options and works with many blogs types and accounts, even at the same time. You also got history of the latest operations done.
  3. Delicious by Yahoo: A life saver, if you use Delicious and the Firefox plugin they suggest you, try this one made by Yahoo, it’s better. Remember to check for the function to hide your local bookmarks menu. If you use other social bookmarking sites, stop here, otherwise use delicious now!
  4. Full Fullscreen: Now if you press F11 you really go fullscreen. If you can remember the next tab/previous tab keystrokes (CTRL+PGUP/PGDN) you can activate the function to even hide the scrollbars and the tab strip at the top. Surfing the web full screen, without any window chrome enhances the experience dramatically. It’s also good for shop stands and demos.
  5. SearchStatus: It adds the Google PageRank indicator in the lower right part of your status bar without the clutter of the Google PageRank Toolbar (you already got the search box, why duplicate it!), along with other commands.
  6. Cooliris Previews: Let’s you peek at a link destination before opening it, good in search engines. Paul Angles from Snap Shots suggested me to check out their extension (also available as a publisher script or as a plugin for many blog types) and I found it good if not better because it also deals with contents (summarizing RSS feeds, for example).
  7. FoxyTunes: You can control iTunes, Windows Media Player, VideoLan, WinAmp and much more, from the status bar of your Firefox. It can even find the lyrics for the song you’re listening. This extension is so popular that if you got it installed, ScribeFire will detect it and post the song you’re hearing when you send the blog article!
  8. Greasemonkey: This is the queen of all extensions. It’s difficult to explain, but very useful, for developers and also for normal navigation. It modifies a page, adding a function it was not programmed to do, on behaviour of sets of commands loaded as a scripts. To make it simple, you can have it overlay the Google Image results instead of loading it in another page, make your favourite website fonts always bigger than others and so on. The extension itself does nothing, you will need to load some scripts for it from their repository. It’s worth the five minutes exploring it, and you can even write your own scripts because they are written in plain Javascript.
  9. StumbleUpon: The extension is really nice, I found out I don’t use it anymore because you can’t have its toolbar show up only if you need it (it opens up each time you open the browser, maybe it’s a bug). Works this way: you make an account on the website, install the extension, then the toolbar appears and you can "Stumble" on new sites with the click of a button. It’s like zapping on a TV, and you can provide even a feedback by clicking on the thumbs up/down buttons.
  10. DownThemAll: This is a download accelerator. Indeed, I really don’t understand why the standard Firefox download window hasn’t operation persistance (you can’t resume a download if you closed the browser or it crashed) and sometimes files doesn’t resume at all if they stop downloading. I tried many pieces of software, I found out that it’s difficult to find a good download manager that is free, works with Vista, doesn’t try to "force" you to use it, and works in Firefox without other extensions or plugins to install. DownThemAll has all the aces on his hand, and some more, like for example the ability to download each file of a type on the same page (a leeching feature!?) and much more.