Firefox essential extensions

After using Firefox for a while, it's hard to imagine still how "normal people" surf the web. By now, I tweaked my Firefox behaviour with several extensions.
Webdeveloper toolbar
Essential for developing web pages! The toolbar offers too many options to list all, but to name a few that I would not live without anymore:

• CSS tools: edit the style sheet of a page on the spot, great for testing and debugging. Mark links as visited or unvisited to test styles here too.
• Clear HTTP authentication or session cookies: means not having to restart the complete browser to test the start of sessions and such.
• Resize the window to any format, to see how things look at good ol' 800x600.

Tabbrowser Extensions
The Tabbrowser Extensions by Shimoda Hiroshi are an important tool to make Firefox really work completely in a single window, with all browser tabs neatly organised. The extension offers a lot of finetuning to open new tabs for links to other sites, search queries, and so on.
Linkification
Listed with other extensions, this one looks at your page after loading, and "fixes" the web and email addresses that are not yet clickable links. Too often, someone refers to an interesting resource but without linking to it.
BugMeNot
In the same list: getting tired of registration forms just to see a single item that is free anyway? Reclaim your privacy. Install this extension, and with a simple right-click it's possible to query the BugMeNot database for an account someone else already made. Maybe it doesn't work, try again for a different account. Maybe there is none available, then you still have to create an account (and add it to BugMeNot, to perhaps save someone else the trouble).