Gerry Pugliese, a self-declared "huge Mass Effect fan," has finished work on a 400 page rewrite of the last game in the series. Called Mass Effect 3: Vindication he describes the project as "a fan revision, and blueprint, for fixing Mass Effect 3."
Vidication includes new additional characters, romance options, missions, and more. The project is book rather than a game or mod so you'll need to read through the changes rather than play them. Pugliese revised key plot points, character interactions, and the controversial ending of the game.
Pugliese comments:
"The endings are a third of ME3V and I've created more than ten new ending scenarios including having Shepard and friends survive, and going on to live happy lives; or Shepard succumbing to the Reapers' power, turning evil, and enslaving the Galaxy, and turning many major characters into Reaper minions to serve at his/her side."
He adds that he wrote Vindication in part because he hopes to work in the games industry.
You can read all of Vindication below or download it directly here. Mass Effect 3 was released in March, 2012 and BioWare is actively developing the next game in the franchise.
MassEffect3Vindication-v1-1.16.14-GerryPugliese