...
IEView
Gmail Space
DOM Inspector
Reveal
Fission
Tab X

i use

stumble
cute menus
Ie tab
online gamers toolbar
image zoom
Dom inspector

These are great espcially stumbleapon it is good when you get bored!

I only really use stumbleupon apart from that i don't really use the extensions much

Add Bookmark Here 0.5.5
Add N Edit Cookies 0.2.1.0
All-in-One Sidebar 0.7 RC 4
BBCode 0.4.1.3
Classic Menus for Winstripe 2.5
Clippings 2.0.1
ColorZilla 0.8.3.1
Console² 0.3.6
DOM Inspector 1.8.1
Download Statusbar 0.9.4.1
DownThemAll! 0.9.9.6.5
ErrorZilla Mod 0.1
Extension Manager Extended 2.5.1
Forecastfox 0.9.3.1
FoxyTunes 2.0.2.1
Google Pagerank Status 0.9.5
Google Toolbar for Firefox 2.1.20060807W
Greasemonkey 0.6.5.20060727
Html Validator 0.7.9.4
IE View Lite 1.2.5
InFormEnter 0.5.1
JavaScript Console Plus 0.1.2005042201
Live HTTP Headers 0.11
MinimizeToTray 0.0.1.2006030906+
Nightly Tester Tools 1.2
Patch for bug 327604 3
Performancing 1.3
Popup Count 0.3.2
SEO For Firefox 2.0.3b
SessionSaver .2 0.2.1.030.4
Show Failed URL 0.1.4
Stop-or-Reload Button 0.2
Talkback 2.0
TimeStamp Converter 1.3.4
Undo Closed Tabs Button 1.9.6.1
undoclosetab 20051204
User Agent Switcher 0.6.9
Web Developer 1.0.2