If you still like to read content on paper and you tend to print out web pages for future reading, then you will love Clippable. It’s a free Firefox and IE add-on that cleans up a webpage so that when you print it, you only get the content and not the other junk.
Make a Webpage Printer Friendly
Have a crapload of bookmarks in Firefox? By default, there are not many options for sorting bookmarks in Firefox. Luckily, there are tons of add-ons. SortPlaces is an awesome one that lets you sort by different criteria automatically.
Sort Firefox Bookmarks By Name or Folder

We love this icon and use it to replace the default one on our quick launch. Bravo to Daemon of DeviantArt. We did have to convert from .png, see Imagicon
Download the .png @ DeviantArt

MozBackup can backup and restore your Firefox bookmarks, passwords, stylish.rdf settings, extensions, themes and much more. Never worry about corrupt profiles again ! Works with Thunderbird and Flock too. Our all-time favorite Firefox backup tool.
MozBackup Homepage
Do you use the Ctrl+F shortcut key combination to find things in a page often? Now you can make Firefox save them.
FindList

Tabberwocky is everything you might want in a Tab Manager for Firefox. From locking tabs to allowing multiple rows of tabs, this thing does it all. And at 25K, it’s considerably smaller than Tab Mix Plus (~400K). For you keyboard commando’s, there are shortcuts for nearly everything.
Tabberwocky
Hate those pages that automatically refresh every couple of minutes? We do too. If you are using IE, just head to Tools –> Options, go to the Security tab, click Custom Level, then find Allow META REFRESH and disable it.
Want the same thing in Firefox? Lifehacker has the answer: head into about:config and change accessibility.blockautorefresh to true.
Ever wanted a customized folder on your Firefox Bookmarks bar that just shows whatever bookmarks that match your search terms?
Open up the bookmark organizer (Ctrl+Shift+B), do a search through your bookmarks, click Save, give it a name, and then drag the new search bar (at the bottom of the Bookmarks Menu) over to the Bookmarks bar (or wherever else you want it).
If you want the Firefox Awesome Bar to give you search suggestions, act as a calculator, or add a spell-checker directly in the list without needing to waste time hitting the search results page, the CyberSearch extension is exactly what you need. Hit the download page for way more screenshots.
CyberSearch