What online FPS(s) do you play, and do you feeling like having a "friendly" game sometime if a few people have said games? If not enough people have the same one, then I guess we could just use the MoHAA demo:
http://www.eagames.com/official/moh/alliedassault/us/download/demo.jsp
Or the Battlefield 1942: Secret Weapons of WWII demo:
http://files.filefront.com/Secret_Weapons_of_WWII_Multiplayer_Demo/;940664;;/fileinfo.html

(I'd go with BF1942)