It seems like everyday there is a new extension created for Firefox. 
Although some of these are quite cool, I try to avoid rushing to
install them, as at the end of the day I don’t actually need them.

It’s
a shame that everyone seems to focus on the newest and shiniest
extensions, so I’ve decided to take it upon myself to promote some of
the lesser known extensions that I believe really make Firefox a joy to
use, rather than just something to show off to non-Firefox users who
haven’t seen the light yet.

1. Download Statusbar – view and manage downloads from a tidy statusbar, so that downloads don’t get in the way of browsing
2. Colorful Tabs – May sound really boring, but it makes it a hell of a lot easier to distinguish between tabs
3. Image Zoom – This is one of my personal favs as it allows me to zoom in on images on a page without having to download them
4. PDF Download
– For all those annoying sites that seem to grow and grow where they
are worried about you stealing their content. This extension allows
PDFs to be opened in a tab for easier management
5. Tab Mix Plus – Every tweak and option under the sun you could ever want to manage tabs
6. WebmailCompose – Fantastic extension that opens your chosen webmail compose window if any email addresses are clicked on
7. Optimoz Tweaks – If you a heavy user of sidebars this great extension makes it easier to open and close them
8. Foxmarks Bookmarks Synchronizer – The only bookmarks sync tool I’ve found that works seamlessly between PCs
9. Autohide
– This one isn’t promoted heavily, but if you like browsing full-screen
it gives some useful control over what elements Firefox displays
10. MediaPlayerConnectivity– automatically launches all media elements in their correct players, allowing full-screen playback of embedded videos

I’m sure there are many others that people can’t live without, but these are always the first ones I install on a new PC.