I do a lot of blogging while on line so I have a set of Add-ons I found to be very handy for blogging. I am also picky about the way things look so I have add-ons for that as well.
All-in-One Sidebar - Nice way to keep my add-ons and downloads where I can access them easily
Autocopy - great for copying text from websites by simply highlinghting it - not working with 3.6 at the moment.
Cool Previews - It helps not having to click a link to open a page just to see if it's what I'm looking for.
IE Tab - Not working with 3.6 yet so have Coral IE Tab for now
FEBE - Great Add-on and Firefox preferences backup
Lazarus - Ever typed a long post only to have the browser glitch and lose everything you wrote before it posted? Not anymore with this add-on.
Read It Later - Great way to go back to a page when looking for new material to blog about.
Screengrab - when you just need that screen as an image at the moment
Tab Mix Plus - love all the tweaking I can do with my tabs
Text Link - so when you find a site address that is not clickable on a page, now it is.
Xmarks - the perfect bookmark backup
United States English Dictionary - comes in very handy when typing too fast.
There are the ones I use mostly for blogging, others are to simply make some sites look better like Google.