RadiusIM is an instant messaging website that lets you know the location of your friends. You can talk with your contacts on either MSN, AIM/ICQ, Yahoo and Gtalk/Jabber. What is great about RadiusIM is that you do not have to download anything, so you can access it from literally anywhere.

When you log on to the website, you will first select your location. Your IM buddies will then be displayed in the Friends List as pictures in a map. You can zoom the map to any place you want in order to see other people from that location. The windows can also be resized according to your liking.

Image source: RadiusIM