Adblock - Get rid of those ads in web pages
Allow Right Click - Stupid web masters won't stop me!
Basics - I like having a new tab button
BugMeNot - No web registration
ColorZilla - Cool little eyedropper in FireFox
CuteMenus - Adds Icons next to the context menus
Download Statusbar - Much better than that download manager
Minit - Reorder tabs, really nice
Popup Count - See how many have been blocked
Popup Alt - See those alt tags
Reload Every - Add meta refresh to any site
Session Saver - If you don't get anything else, get this. It saves your tabs and history/location in each one and restores them on start, even after a crash. Don't use multiple windows though, it only saves the last window closed (includes things like dl manager and extension manager.)
Spellbound - Spell check your forms before submitting. (Needs to be better integrated.)
Target Alert - See what it is before clicking on it. (Still slightly buggy)
Text/Plain - Make a URL in plain text a link by highlighting it
Titlebar Tweaks - Change how the title is displayed for pages
Tweak Network - Use that broadband connection
User Agent Switcher - Useful for those pages who want only IE
Weatherfox - See what's going on outside your cube
Web Developer - Helps deconstruct your website so you can build it correctly
Best part of extensionmirror.nl is that they usually have extensions repacked for the current FF version even if the author hasn't done it yet.
Oh and for those keeping track, I do have a few more extensions, but they are not listed on this page, so I'll post them separately.