BuddySpace is a Java application which allows optional maps for geographical & office-plan visualizations in addition to standard 'buddy lists'". Looks like a really good implementation of locating buddies on maps. This could be the world, a region, or even just an office. This would be great for when you're trying to locate some wandering co-worker, or even find out where a friend is chatting you from.

frank569 > "Hey heo, what's up?"
heouser > "Hey Frank, how's it going? Woah, you're just down the street from me, why don't we meet up at the park?"

BuddySpace is cross-platform and seems like a decently implemented chat client in itself. Being built on Jabber means it will work with Tiger's iChat.