The real power in global financial markets rests with "institutional investors", the professional speculators:
Commercial banks: The traditional big boys of the financial world, commercial banks' basic business is retail: to pay depositors less interest than they take from debtors. In addition, they've been major investors in bond, currency and equity markets for over a century, although their market share has declined with time. (Example: Citibank, National Australia Bank.)
Investment banks: Otherwise known as merchant banks, investment banks don't handle ordinary accounts but rather act as intermediaries for companies wishing to float on the stock exchange, issue bonds, arrange syndicated bank loans or buy other companies. They also speculate heavily in financial markets on their own account. (Example: Merrill Lynch, Goldman Sachs.)
Managed funds: The new big boys on the block, managed funds include both private and public pension funds, which invest heavily in securities, and mutual funds (unit trusts), in which investors pool funds in order to acquire greater market leverage and thus returns. Together, managed funds account for two-thirds of all equity owned by institutional investors in the US. (Example: Bankers Trust, AMP.)
Hedge funds: The sharks with the sharpest teeth, hedge funds are private investment partnerships, generally between groups of super-wealthy individuals and other institutional investors, which engage in especially high-risk speculation. Blamed for igniting the world financial crisis of 1997-97, hedge funds went into temporary decline but are now on the rise again. (Example: George Soros' Quantum Fund, Long Term Capital Management.)
Corporate finance departments: So lucrative is speculation that the treasuries and finance departments of many non-financial institutions are putting serious money in, either in order to protect against risk or for purely profit-making purposes. (Example: GE Capital.)