Useful Extentions which have worked great for me.

• Google Preview
• DownThemAll
• GmailSpace
• TabMixPlus
• Video Downloader
• Download Status Bar
• AdBlock Plus

These extentions make firefox the best browser in the world to use! DownThemAll is for when I want to download all the pictures on a website Im on one go! Google Preview lets you see a preview of the page in google search. Gmail Space lets you use your gmail as a online storage! Pretty smart! TabMixPlus gives your tabs everything you might want in tabs, and it saves all your sessions so just in case it crashes and has lots of useful tools for use with your tabs! Video Downloader lets you download google video, you tube, or any other online video content provider. Download Status Bar is the best thing I found, since before the Download Window for Firefox would freeze my window or slow it down immensely, but now its like nothing it being affected, I love it! AdBlock Plus was a huge improvement when it comes to blocking unwanted pop-ups!

With all these extentions you customize firefox to your liking!