When I worked for British Telecom, we had nice simple internal Usenet newsgroups. Some specific to particular business-related areas (like programming), others hobby-based (cycling, swimming, etc.) and some just for general chit-chat. No need for any expensive social-networking websites or anything like that, just a simple Usenet server buried in a data centre.
It used to be a great way to get to know colleagues all over Britain, as well as a terrific resource when you needed help getting something working.