I’ve been using Firefox add-ons for years now and now dwindled down to the ones I used most often:
- ColorZilla (grab color from any web site)
- Ctrl-Tab (thumbnails of all open tabs – kinda slow when you have a bunch of tabs open)
- Drag & Drop.io (very convenient file sharing)
- Firebug (makes CSS infinitely easier to work with)
- GMail Manager (quickly switch between Gmail accounts without authenticating every time)
- HTTPFox (makes debugging HTTP request/response cycles easy)
- GooglePreview (thumbnail previews of Google results)
- Screen grab! (can grab entire web page, visible area, or just a portion)
- StumbleUpon (tons of interesting sites based on your interests, a nice break from work when i need a few minutes)
- Web Developer (complements Firebug very well – though not using it much for anything at the moment)