I use these extensions in Firefox (1.5.0.2 currently; some may be broken now):
- DOM Inspector
- Image Toolbar (actually, this thing is really annoying)
- Greasemonkey
- Document Map
- Forecastfox
- Aardvark
- Add Bookmark Here
- All-In-One Search button
- BugMeNot
- del.icio.us
- Download Statusbar
- Mimetype Editor
- Tab Mix Plus (better than SessionSaver)
- Plain Text Links
- User Agent Switcher (w/ Googlebot)
- View Rendered Source
- Auto Copy (in XP and OS X)
- EditCSS
- Gcache
- Web Developer
- LiveHTTPHeaders
- Adblock
- ColorZilla
- MediaPlayerConnectivity
- Html Validator (based on Tidy)
- jsLib Lite
- Web Color Names
- Amazon Feed Injector
- View Cookies
- X-Ray
- Wayback
- Nightly Tester Tools
- JavaScript Debugger
- Launchy
- Search Keys
and these Greasemonkey User Scripts:
and these bookmarklets:
and in Windows XP, Firefox Preloader