Lots of companies are making use these days of instant messaging technology to improve inter-employee communications. Some of them are using AIM, which may not be the best idea (unless you're using an 'after-market' client like naim or Pidgin, which can encrypt your messages over the server in the middle), and some are using other technologies, like private IRC servers.

Some of these companies, predictably, are Internetworking companies, or the networking divisions and departments of other companies.