Kind of like the facebook instant messaging system. I'd like it. The myspace one uses the .exe based one while facebook uses the web based one. I like the web based one best but yeah it's a good idea.
PycoIM Web Messenger -link outdated, wm removed-
I didn't program it but it sure was complicated to switch it over to my databases =p
I'll probably be rewriting the messenger as time goes on, and the exe version will be completely made by me.