SCORE is a nationwide network of business mentors. They’re volunteers, and many were in the C-suite. They provide advice on everything from the feasibility of an idea to telling you which expert advice you may need (professional engineers, patent attorney) to detailed experienced advice on franchising. They hold workshops across the country, and if they’re in your area, there is a fair chance their offices are in your local library. This is one of the best sources of small business ideas & resources for the USA, and they're supported by the Small Business Administration.