There's a Wikimedia UK Facebook group here:
http://www.facebook.com/group.php?gid=5678482133
And a Wikimania 2008, London group here:
http://www.facebook.com/group.php?gid=18513693344
The Cape Town team have 56 members in their group... ( http://www.facebook.com/group.php?gid=5479264154 )
If you want Admin status in either of these groups just send me a message.
Tom (cfp)