New York's registry is also free. If there is any chance you will be near New York waters, better to have then not have.
NY will inspect boats they think were in their water.
FYI, New York is 1 year period from the time you register. New Jersey is one year, but expires December 31st, regardless of when you signed up.
New York
http://www.dec.ny.gov/permits/54950.html New Jersey
http://www.nj.gov/dep/saltwaterregistry/index.html