The titles are pretty much self explanatory, per request, here's some brief info.
Maniac Missions
A WC Game were you play the role of Maniac.
WCP Multiplayer
WCP was supposed to have a multiplayer component, but they couldn’t complete it in time. They decided to make a stand alone multiplayer game with the same game engine, but it was cancelled.
Privateer 3
The next game in the Privateer series, probably set in the same era of WCP. I don't know if it would follow the adventures of Brownhair/Grayson Burrows.
Privateer Online
A MMPG game set on the WC universe where you could be a Privateer.
WC Online
A MMPG game set on the WC universe where you could have different jobs, like Confed, etc.
WC Strike Team
The sequel to WCP and WCSO.
Wing Commander & Conquer (RTS Game)
A rumored RTS game set int he WC universe. Just a concept, it could be either in space, in the ground, or both.