If you are not using Firefox extensions, you are stupid.
If you are not even using Firefox, you are beyond stupid.
WebDeveloper is awesome.
I like the latest feature that highlights nofollow links.
Shows the IP of the current site. Includes a nice menu to search for that IP in various services.
Make it go faster.
Create free disposable email addresses and paste them directly in forms.
Useful for downloading flash and other embedded objects.
No more annoying flash. If you want to see it, just click on it.
Convert text to L337, ROT13, BASE64, HEX, URL, BIN, DES and more.