A couple websites with lists of cool math games from A to Z are ZMathGames.com and CoolMath-Games.com. These sites have a wide range of math games.
At CoolMath-Games.com, the games are divided into categories of skills the games help to improve. Try the Feed Fribbit Subtraction game in the addition/subtraction section, Math vs. Monsters in the multiplication/division group, and Coffee Shop in the applied math section.
Math games at ZMathGames.com are rated as "most played" and "top rated." There is a wide variety of games, with something for everyone, ranging from Math101 to Day Trader, in which players manipulate the stock market.