Modular software can be pain - you end up installing tons of add-opns. I recently configured a new desktop box and had to reconfigure Firefox. Here's the lsit of extensions I installed, I'd be interested in comments about better or missing add-ins
- Adblock Plus
This is a tricky one. I get content for free for looking at some ads. Might be a fair deal, but often it's too much. On some sites I allow ads, on others not.
- BetterPrivacy
Prevent Flash Cookies from tracking me
- Brief
An RSS/Atom/... Feed reader
- Certificate Patrol
Notifies me when sites change their SSL certifactes, might prevent fraud.
- Change Rerer Button
I don't like being tracked. At least not always 
- CookieSafe
Firefox's cookie handling is damn limited. With this add-in I can edit/delete single cookies way simpler and easily change the per site settings
- Firebug
Good for fixing broken sites
- FoxyProxy Standard
When switching between company VPN and my local net I need different proxy configuration. With this extension I don'T have to go through the settings
- Greasemonkey
Improve websites according to my interest
- JSON View
Renders json more nicely. Good when working with JSON-based protocols
- NoScript
per-site configuration of javascript and stuff. Some websites have nice JS free versions.
- Open in Browser
Adds a new option to the download dialog to open in Browser as web page or plain text. Useful for files a server sends with a "wrong" header.
- Tab Kit
The wider the screen the more I want to have the tabs on the side. This add-in shows tabs in a sidebar with a tree structure and different colors and such
- Tamper Data
Edit HTTP Request before the browser sends them, initially I've got this for security research, nowadays I use it to work-around issues in bad WEb-UIs
- User Agent Switcher
Maybe switching the User agent every now and then makes tracking a bit harder, certainly it can be nice to get a different view. Many sites have a mobile version which is focussed on the content way mor than the regular site.
- Web Developer
Nice tool for working with HTML stuff
Saturday, May 14. 2011 at 15:31 (Link) (Reply)
Evernote Web Clipper
Only useful for Evernote users, of course. I use it for "archiving" web articles.
Session Manager
Lost too many sessions w/ 10+ open tabs...
Tabs Open Relative
When opening a link in new tab, the new tab will be placed just next to the one your're in. I like having related pages also related in the browser window.
Delicious Bookmarks
(Still) my bookmarking service of trust. Searching alternatives, though...
DownloadHelper
Enables downloading Youtube clips. From time to time I want to have a talk or a documentation available offline for later viewing.
wolfgang
Tuesday, May 24. 2011 at 12:34 (Link) (Reply)
Live HTTP Headers
View HTTP headers of a page and while browsing.
martin