Business incubators have been around since the 1950s. Typically attached to universities, these entities offered a proving ground with back-office resources for fledgling entrepreneurs. Now a new breed of incubator, catering mainly to technology types, is springing up all over the country. These startup hubs offer expert mentorship, resources like office space and legal counsel, and even seed money—-typically in exchange for a small amount of equity in tiny (or even theoretical) companies. The best incubators are harder to get into than the best Ivy League business schools. More importantly, early-stage investors are paying close attention. Here are 10 incubators putting their mark on the Web and beyond.