Play mahjong online
At GameColony.com you can play games of skill only -- play for free or play for $prizes.
According to the statutes of most states in the United States, gambling is defined as: "risking something of value upon the outcome of a contest of chance". (Also see No Gambling!). When you are playing games of skill (as opposed to games of chance) for $prizes, it will be a contest of skill rather than a random coin toss that will determine the winner. Playing the games of skill, therefore, has nothing to do with gambling as the skill factor (as opposed to chance) is predominant here. It's not a 'gamble' anymore -- the more skillful player will win far more often.
When players compete in tournaments or games of skill for $prizes -- it is "competitive entertainment" rather than "gambling". The more skilled winner will eventually prevail and will win more matches, tournaments and $prizes.