Internal Revenue Service
http://www.irs.gov/businesses/index.html
Tax information for US businesses.
NC Department of the Secretary of State
http://www.secretary.state.nc.us/corporations/
The Corporations Division is responsible for the examination, custody and maintenance of the legal documents filed by more than 400,000 corporations, limited partnerships and limited liability companies. The duty of the Secretary of State is to ensure uniform compliance with the statutes governing the creation of these entities, record the information required to be kept as a public record, and provide that information to the public. The Corporations Division acts in an administrative capacity only and cannot give legal advice.
US Patent and Trademark Office
http://www.uspto.gov/
The primary services the USPTO provides include processing patents and trademarks and disseminating patent and trademark information. You can search the stie to find active patents and trademarks.