MekWars is a chat and campaign engine for MegaMek. Players join MekWars servers to find opponents for MegaMek games. MekWars servers can be configured to run campaigns and scenarios - tracking player's units, experience and funds.
An excellent implementation of the BattleTech campaign ruleset. That's not an easy fit.
An amazing technical accomplishment considering the massive scope of the Battletech ruleset and fanbase.