My can't live without extensions are
Internetwifi - connection manager
Chromium - browser without the chrome overhead
my favorite browser which is not yet an official extension
QtWeb (fast full featured browser, half the weight of chrome)
MultimediaXine-Xvesa - plays DVD's, CD's and various other media
DeadBeaf - plays all your CD's perfectly
xfi - works with wfe to view photo's
gimp2 - photo editor (OnDemand)
systemconky plus
xfe - file manager
Xarchiver - handles compressed files (OnDemand)
DropBox - store stuff in the cloud (OnDemand)
SearchMonkey - Another favorite unofficial extension. Although I do like "sudo find / -iname FileName" thas app has way more features.
Officeeditor - reads and writes all text based files and comes with TC
let's see what others are using