American Demographics (adage.com/americandemographics): Just as the title suggests, numerous free reports about consumer demographics in the U.S. nationally and by statistical area.
Internet Public Library - The Census Data and Demographics (ipl.org)/: An especially useful site that has links to information about countries other than the U.S.
Millions of entrepreneurs, be it first-time owners of small and medium start ups or Fortune 500 business conglomerates, use this program and consider it to the best business plan template generator on the open market.
But your idea may be so new that you may also need to talk to potential customers, host some focus groups, talk to an ad agency, or maybe even make a prototype and float it past some people. Be prepared to spend the time. Remember, it's not about the Plan but the Planning.