If you use Pidgin along with Eion Robb's Facebook Chat plugin (http://code.google.com/p/pidgin-facebookchat/), this script is a must-have to avoid distractions from Facebook. (As my review title implies, this script might also be useful if you don't like talking much. ;-)) Solid and reliable, and tweaked to avoid interfering more than necessary.

Four stars only because I can think of some improvements that could be made, such as disabling titlebar flashing and allowing showing/hiding after the page loads.