Czuch Czuckers: I have been through every add-on they do (i think lol) and tried alot like BBW.

Now i only really use:

Greasemonkey, for use with hexkids script.

Resizeable Textarea, lets you make the text boxes we type in here any size you want, great for writing large stuff.

Forecastfox, like BBW says, great weather add-on.

del.icio.us, great for storing bookmarks, and also able to access them from any pc.

Gmail Manager, great if you have a Googlemail account.

Perma Tabs, lets you make tabs permanent.

Some others that i use just for fun:

Footiefox, Clear cache button, Colorful Tabs, Fireform, No Go button, Searchbar Autosizer