Sarcasm is an adjusted stress reaction.

sajee asked for our favourite Firefox add-ons.  Here are mine, plus a few other bits and pieces that I can't live without:

1.  LJ addons.  Confusing name, confusing interface.  But it has some useful points: it notifies you when your flist updates, enables comment unfolding even for unpaid accounts, unfolds cut-tags without the tedium of opening another page, randomly selects userpics, and various other things that I don't really need. 

2.  Adblock Plus.  Maybe I should have mentioned this first?  Anyway, it doesn't block all ads, but it helps.  Particularly useful in suppressing pop-ups.

3.  Download Statusbar.  Condenses downloads into a single handy status bar.  Much less clunky than the separate download window!

4.  DownThemAll!: A really useful download manager/accelerator.  Can be used with free Mediafire accounts, too.

5.  Flashblock: Replaces flash with a clickable icon.  Includes options to always allow flash from a chosen site, but every now and then I think of replacing it.  It gets a bit annoying on flash-dependent sites like YouTube.

6.  LJ Login: This isn't actually an official Firefox add-on, but I've never had a problem with it.  Lets you switch between LJ accounts with a couple of clicks, which is handy if you're running a sockpuppet.  *eyedart*  Or roleplaying, or moderating a site with a single mod sock.

7.  Net Usage Item: For those of us in danger of using up our download quotas -- this tells you what percentage of you're quota you've used.  The House o'Squid depends on it, even though it frequently leads to discussions that go, "32%?  HOW CAN WE BE AT 32% IT'S ONLY BEEN A WEEK WHAT THE  HELL HAVE YOU PEOPLE BEEN DOWNLOADING????!!!"

8.  Tab Mix Plus: Features a session manager, a facility to undo closed tabs, marks unread tabs, and generally makes itself useful.

9.  TinyURL Creator: ...Does exactly what it says on the tin.  Handy for Twitter, which brings me to...

10.  TwitterFox: Runs Twitter as a small pop-up in the corner of your browser.  Unobstrusive, attractive and handy.  I didn't really start using Twitter until I got this.

11.  WordCount Plus: Tells you the word count in selected text.  Handy if you (a) use GoogleDocs and (b) like to obsess over wordcounts.

I also use a couple of Greasemonkey scripts, but the only one I have active at the moment is one that removes a permission clicky thingie from Gmail when you're replying to comments.

In terms of other nifty tools, I really like KeepIt!, which lets you save YouTube videos in a couple of file formats, and LyricsWiki, which is just plain handy.