New York [BusinessWeek Online] Depending on who you believe, ethanol is either crucial to weaning the U.S. off foreign oil or an overhyped fad surviving on generous government subsidies. But even as the plant-based fuel is becoming a more important ingredient in the American gas supply, there have been few opportunities for investors to bet on ethanol’s prospects. All that is about to change. Three Midwest ethanol companies have recently filed to go public — Aventine Renewable Energy, VeraSun Energy, and Hawkeye Renewables. … These three companies heading for IPOs may be investors’ best chance to bet on what could be the fuel of the future.