Some other very worth while extensions are:
BBCode - Adds BBCode to the context menu for forums.
BookmarkSynchronizer - Sync your bookmarks across all your computers. VERY USEFUL!
downTHEMall! - Download all images on a page based on their extension and other settings.
AutoMarks - Use the location bar to autocomplete URLs from your bookmarks! VERY USEFUL!
Image Zoom - Adds zoom functionality to images
Tiny URL - Easily create TinyURLs of the page your viewing from with in firefox
CopyURL+ - Copy the URL of the current page along with the title or the selected text.
FirefoxView - If you still use IE sometimes this will allow you to select a link to open in Firefox.
Sorry, I don't have time right now to grab the links for all of them so you'll need to google their names.