Just a quick note - I've fixed my
LJ Friendsmap tool, which scrapes the location info from your friends' profile pages and then assembles their locations on a Google Map, so that it now supports communities as well.
It's still slooooow, and doesn't update you while it's working, so be warned, it may try your patience. Gets there in the end, though. (Or at least it should. Send me an email if it doesn't.)
Scroll down to the bottom of the home page for a link to the code, which is GPLv2.