Version 3.1

You can log out of Facebook Chat and still see who is online. Updates every 60 seconds. You can Show or Hide each of the options using Greasemonkey's User Script Commands

PopUp Friends
Display online friends on top of Facebook Chat

Click the title to show/hide the list and click x to remove altogether.

Friends (x)
Adds an indication to the top Friends link in the header

DropDown Friends (Old Facebook only)
Adds the list to the drop down friends menu

Lefthand Friend List (Old Facebook only)
Adds a list of online friends to the sidebar in place of the ads

Modified version of
http://userscripts.org/scripts/show/19450 and http://userscripts.org/scripts/show/23499

DISCLAIMER: This may violate Facebook's Terms of Service. Responsibility for any violations is held by the user, not this author.