I love Firefox3 - use it exclusively under XP, Vista and Ubuntu except for exceptional purposes when I may use google Chrome (beware!) or Internet Exploder (beware!) or Opera (Oh why did they do what they have done to the interface!
If you are using FireFox and have not got the noscript add-on installed then install it and use it. Makes for the safest and most private browsing.
Other add ons I recommend:
CoolIris, formerly PicLens: Allows you to search for images and videos on various sites and gives the results on a Fullscreen 3D wall you can haul around to look at pages of images real quick. Has many functions when you get into it and makes image and video searching a pleasure.
FastDial: When you open a tab you are presented with your own user defined favourite pages as thumb nails. You can decide how many rows and columns there are and place your most visited sites in the thumbnails. One click new tab 2nd click probably where you want to be: invaluable time-saver and type-saver.
Fast Video Download: Instead of watching video's on youtube or almost anywhere else why not download them to your hard-drive? Especially for those you view often.
Anyone else found some great Add-Ons or Plugins for FireFox?
CrazyB