Numerous different systems. If you want to look at modern, developed economies, Worker Co-operatives are smaller, Socialist entities that have far more equitable distribution, happier workers, and more stability. If you want a more Libertarian approach, EZLN doesn't seem to have very high disparity, a bulk of the wealth is owned by the Workers, though they reject terms like Socialism. At the risk of being called a tankie (I'm not, I am incredibly critical of more centralized Socialist projects), even the USSR had far lower disparity during it's time than Tsarist Russia or the current Capitalist Russian Federation.

The answer is for Workers to share the Means of Production in a democratic fashion, as opposed to having petite dictators focused on accumulating Capital.