Best Firefox Extensions

This is an attempt to list the best extensions for the Mozilla Firefox web browser. Extensions are mostly available from update.mozilla.org.

Killer

AdBlock makes a huge difference after only minimal set up.
All-in-One Gestures provides a heap of useful gestures.
Web Developer as the name suggests, not much good if u are not a web developer.

Download Status Bar instead of a window, tidily shows downloads in a bar just above the status bar.
Tabbrowser Preferences in particular, the option to force the shell to open tabs rather than windows.
Super Drag&Go drag any text to go to that URL or google that text; drag an image to save it.
Linky open all selected links in tabs, open all linked images in tabs, etc.
FastDic / DictionarySearch / Dict high-speed dictionary lookup (u can usually add in google, acronymfinder, etc).
Copy URL + gets the page title, URL and quotation all at once.
Text Link / Linkification convert plain text URLs into clickable links (linkification seems to suck performance when on by default).

FireFTP a reasonably good FTP client.
ChatZilla a lightweight IRC client.
Sage an RSS reader.
QuickNote a sort of integrated notepad, handy autosaving and autocopypasting.
Mozilla Calendar a calendar.

MiniT allows drag and drop tab rearrangement.
undoclosetab speaks for itself.
TargetAlert puts an icon next to links that open PDFs, Word, mailto, new windows etc.
Gmail Notifier displays your new Gmail count in the status bar, one-click access to your inbox.
FlashBlock replaces flash objects with an 'activate' button.
GooglePreview shows a thumb-shot page preview by each google result.
FoxyTunes allows control of winamp (and many others) from within Firefox.
Download Manager Tweak makes the default download manager a lot better.
Spellbound a spell checker.
BugMeNot provides logins to free-register sites like NYTimes.
Session Saver Remembers tabs/history when Firefox is closed/crashes, then restores them on restart.
IEview opens pages in IE - good for IE-only pages, particularly useful for web developers for testing.
Paste and Go go straight to a URL from the clipboard.
Stop-or-Reload Button fuses the stop and reload buttons into one, a la safari.
Menu Editor allows full customisation of the right-click context menu.
BBcode handy formatting if u use a phpBB forum.
Show Failed URL displays failed URLs in the Location Bar when XUL error pages are enabled.
Nuke Anything feel the power.
HTMLtidy Validator handy validator program, integrates with View Source.
down Them all / Magpie bulk saving images, etc.
mozFBRH adds middle-click to things like the back button.