Hattrick is a free-to-play browser based soccer management MMO game. The player can recieve a team in one of the nations lowest playing leagues and can try to rise to the top of premier league.
The depth of this game is astonishing. You can configurate the training, add specialists (like co-trainers, PR-manager, pyschologists etc.), create your own team-dresses, build your stadium, shedule freindly matches against other players teams and play the regular league matches to try to rise within the ranking system.
128 different countries are participiating in the game already, and each season, new ones join the club. League games are played on weekends and players can follow the game with a live-feed.
You can read more about this game at: http://www.hattrick.org/