A wonderful New York Times graphic showing the global flows of sovereign wealth.
A sovereign wealth fund is a huge heap of money that is controlled by a nation -- say Singapore or Saudi Arabia -- rather than by a private transnational company. The latter is called private equity funds and their investments have been prime movers in global finance for decades. Some of the largest banks and finance companies that are in the current news cycle, like Bear Stearns, or UBS, are good examples of private money. They buy and sell business across national borders.
According to the New York Times in their article The Leveraged Planet, the amount of sovereign controlled wealth is expected to rise to $12 trillion by 2015. These funds also buy and sell businesses across borders but since their owners are other nations, or nation-state organizations, the implications of their scale and intent are proving enormous.