Here are a few references, in no particular order, to web pages of particular
interested to network game programmers.
Game Networking API's
If you know of any other game networking API's on the web, please send
their URL to firstname.lastname@example.org.
Online Game Networks
Note: many search engines list game networks.
For example, www.itf.org has a good list.
Military-based Simulation Networking
Other sites of interest