My favorite Firefox extensions:

super drag&drop -- Updated for Firefox 1.5+

• Drag a selection for google search
• Drag a link to open in a new tab

TextZoom -- Updated for Firefox 1.5+: fixed a bug for not zooming when open the first new tab.

• Set a fix default zoom size, useful for high-resolution screen
• (Using the minimum font size setting can not display some pages correctly)

All-in-One Gestures

• Mouse gestures: never need to click back and forward button!

Download Statusbar

• The "Downloads" window of Firefox is quite slow and obtrusive sometimes
• This extension shows the downloading status friendly

FlashBlock

• Opened too many tabs? Use this ext. to block the CPU-hogging Macromedia flash!

IE View

• Anyway, the world is not perfect and the websites are not all Firefox-friendly
• Use this to view pages in IE :(

ForecastFox

• Weather is quite important when I was riding bike to the school :)

ResizeSearchBox

• Who designed the search box? so small! -- now you have a better solution.

Adblock + Filterset.G

• Block ads in an easy/lazy way