The Battle Cat's Marathon Page - Find original Marathon maps, films, Forge tips, and related humor here. - http://www.webwonks.org/Marathon/Marathon.html
Marathon's Story - Houses the full text of the game series with discussion and speculation. - http://marathon.bungie.org/story/
10/5 Mapmakers - Offering map downloads and information on the OBED Marathon level editor. - http://www.numbera.com/105/
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." - http://www.gamespot.com/pc/action/marathon2/review.html
Marathon Infinity - Official site - http://www.bungie.com/products/infinity/infinity.htm
Marathon Open Source - Microsoft's own Open Source Initiative, using the GPL'ed Marathon 2 source code, called Aleph One. - http://source.bungie.org/
Marathon Arena - A total conversion for Quake 3 Arena in the spirit of Marathon Infinity. - http://ma.bungie.org/