UPDATE AUGUST 3, 2014
Its official, with the death of former GAMESPY master servers, the in games server browsers no longer works for these wonderful games of 12 years.
AHHHH ! BUT ITS NOT DEAD YET THE MULTII-PLAYER LIVES ON!!!
You will now need to follow the instructions here to join on line servers that are sill running and populated with people playing.
http://bur-clan.com/connect-and-play/ - has their own tool / mod to join their servers or those you know the IP Address to for quick connection.
BUR has an unofficial patch that makes the in game server browser work again through Q-tracker, I suppose cracked .exe, unfortunately it dose not work with the GOG DRM free version. because of the original MOHAA.exe version not being identified. Contacted BUR hopefully they can fix it.
Or use free QTracker (consider purchase)
Or
http://www.gametracker.com/ sign in
Allied Assault
http://www.gametracker.com/search/mohaa/
Spearhead = MOST ACTIVE
http://www.gametracker.com/search/sh/
Breakthrough
http://www.gametracker.com/search/bt/
Use as the the server browser and connect to the servers through these other services.
Hope to see you soon! Its not GAME OVER!
PLEASE GOG, DO NOT LET EA REMOVE THIS GAME FROM BEING SOLD HERE.
PLEASE TRY AND CONVINCE THEM, THAT THERE IS STILL ONLINE GAME-PLAY AND COMMUNITY GOING ON OUT HERE WITHOUT THEM . MP WAS AND STILL IS AN INTEGRAL PART OF THIS CLASSIC GAME.