Americans for the Arts has a wealth of policy related resources on their site.
The Center for Arts and Cultural Policy Studies at Princeton University.
CPANDA, the Cultural Policy & the Arts National Data Archive, is the world’s first interactive digital archive of policy-relevant data on the arts and cultural policy in the United States.
The National Assembly of State Arts Agencies provides support and information on issues of policy, advocacy, and state agency initiatives.
The Urban Institute provides access to many research reports regarding arts policy in the United States.