10/5 Mapmakers
Offering map downloads and information on the OBED Marathon level editor.
GameSpot
Chris Hudak review [8.2/10] includes screenshots and downloads. "A distance runner, and with all its perks and goodies should more than tide over the 3-D shooter fanatic."
Marathon Arena
A total conversion for Quake 3 Arena in the spirit of Marathon Infinity.
Marathon Open Source
Microsoft's own Open Source Initiative, using the GPL'ed Marathon 2 source code, called Aleph One.
Marathon Resurrection
A total conversion for Unreal Tournament in the spirit of Marathon, by Team Unpfhorgiven.
Marathon's Story
Houses the full text of the game series with discussion and speculation.