OB-1
Use this application to check if your co-workers are available for chat/discussions etc. It uses IP Multicasting, so there is no central server. Just run the program, and everyone in the office sees you on their list. There is also an option to create tunnels to offices at remote locations.
You can download the beta version right now. I'd like to hear how this software performs at your workplace. The only system requirement is that you should have winsock 2.0 installed.
Download - OB-1.exe (59 kb)