Color picker - get the HTML code for colors (plus a few other things)
http://www.iosart.com/firefox/colorzilla/
Image zoom - zoom in and out of images
https://addons.mozilla.org/en-US/firefox/addon/139
SearchStatus - see Alexa ranking + Google pagerank
http://www.quirk.biz/searchstatus/
FireFTP - ftp client for Firefox
http://fireftp.mozdev.org/