Every Secretary of State office in the US

Here's a link to a directory of all 50 states' Secretary of State sites, where one incorporates.

Statistics on the number of incorporations by state

On the International Association of Commercial Administrators website's page for annual jurisdictional accounts: under 2008 Annual Report, there is a link to a Search by Jurisdiction Online. From there, choose United States and, e.g. New York, choose BOS Annual Report, and Display Report. The page opens to show the number of corporations filed during the past two years, along with the total number on file as of the last two years. They also have full pdf files for previous years.