Here's a list of addons that are awesome for Firefox. Maybe I'll format it better some other time! To add these addons easily, select Tools->Addons, and pick Get Addons, then just write them in the search field.

Security:

WoT - Web of Trust
This addon is basically a must-have. When you do a google-search you'll get a green ring on most sites just behind the link.
Red rings however means that you should stay the hell away from those sites! Everyone can rate sites, and users are a strong tool to measure security, the ensure things are up to date.

Adblock Plus
Blocks alot of ads from various sites, but has a tendency to bug sometimes (at which point you have to do some clicks to allow adds on select webpages). Might be a hassle at times, but for geeks like me who don't mind a little bit of hassle it's no big deal!

BetterPrivacy
Removes so-called Super-cookies when you close Firefox. These cookies are used by for instance google to track your activity long-term, and aren't removed when you remove cookies with the Clear Private Data-option as far as I'm aware. Antispyware-programs and CCleaner tends to react on these cookies.

NoScript
Incredibly useful and incredibly annoying at times. Blocks scripts from running except from sites you choose as safe. Can save you when you accidentally open an unreliable site.

Awesomes:

Cooliris
Is just generally awesome. Search for images in google and click a button on the toolbar and you get a huge sliding screen with all the pictures the search returns. Has to be seen!
Here's a movie of it in action: http://www.cooliris.com/?s=1

Interclue
Shows the content of links before opening them. Sort of a mouseover-thingy, quite handy.

Speed Dial
This one is awesome. You basically get a grid of nine buttons when you open a new window or a new tab in firefox (can be set to tab only if you like your homepage) containing shortcuts to sites you choose. Whenever you click CTRL+1-9 you open one of these sites, so I for instance open a new tab each day and click ctrl+1, then ctrl+2, then ctrl+6, to open the two forums I visit and my favorite news-site.

Usefuls:

DownloadHelper
Lets you download youtube-videos and such. Not much more to say, get it if that's interesting to you.

DownThemAll!
Download manager, can theoretically speed up downloads.

IE Tab
If a website is completely weird on firefox (rare nowadays), this thing lets you open a site in internet explorer from your firefox (it loads the engine into the window/tab).

Lazarus: Form Recovery
If you write a post, and click send and get an error or if firefox crashes, this thing can be used to recover what you wrote. Luria might need this one.

Great post Cooliris looks awesome Havent tried too many addons, but Adblock plus is a must have

Resurrecting this thread:

WoT - Web of Trust

http://www.mywot.com - Download from there or by searching in the extensions-window on firefox.

This addon is basically a must-have. When you do a google-search you'll get a green ring on most sites just behind the link.
Red rings however means that you should stay the hell away from those sites!

What makes this addon awesome is that users like ourselves can rate sites, which ensures it stays more or less up to date.
This is a security-addon I'm pretty confident most people here would want, considering we're a crowd that bad people want to steal passwords from.

Copying above info to original post!

On a related note

http://www.malwarebytes.org/

download their latest anti malware programme and watch it a discover shit

(a) quicker than norton, kapersky , macafee etc.
(b) Watch it kill it ALL with just a system reboot

I cannot stress exactly how efficient this bad boy is.

itte