Firefox: KeeFox brings tight integration between the cross-platform, open-source password manager KeePass and Firefox, providing automatic logins, form filling, and more.
Firefox/Chrome: Sure it's nice and all that we get Gmail for free, but those ads to the right of open messages aren't really all that helpful. Free browser add-on Rapportive replaces Gmail ads with contact info about the sender.
Firefox: Sure it's fun to hunt for deals online, but it's even better to be alerted when an item you want is at its lowest price. Ookong is an Amazon.com price comparison tool you can use to track price histories.
Firefox: If you hate having to search through your folders every time you change the type of file or directory you're saving to—and we certainly do!—Save File To helps you make custom context menus for file saving bliss.
Firefox: Maybe you've seen your favorite extensions fall behind when new Firefox releases roll out, but you haven't known what to do about it. A new-ish Mozilla add-on not only enables technically incompatible extensions for testing, but makes reporting actual incompatibilities easy.
Firefox only: Clicking through multiple product images while shopping on Amazon is really a chore. PictureFox, a handy Firefox add-on, opens all the images in a single gallery so you can stop making with the clicky-clicky all the time.
Firefox: Every new version of Firefox offers enticing new features, but the real question is whether or not your beloved Firefox extensions are ready for the jump. Is It Compatible? puts the compatibility information right in your add-ons window.
Firefox: If you've ever started up Firefox after a system crash and had it attempt to restore all the eleventy-billion tabs you had open, you know what a resource drain your tabs really are. BarTap helps alleviate the stress.
If you're looking for a way to organize all the information you find and research you do online, and you've had enough with bookmarking, copying and pasting, and cobbled-together techniques not cutting it, Zotero is a comprehensive information manager for Firefox.