Realtime chat engine
jaddison: Ummm... your own IRC server?  Seems pretty realtime to me, and quite configurable.  Of course, IRC is geared towards group chat, not user-user.Perhaps include some more details about what your restrictions/requirements are - will the users be web-based?  How many concurrent users will you expect online at any given time?If you're looking for advice from others, it's best to provide as much info as you can.