National Assessment Governing Board (NAGB)
http://www.nagb.org/

The National Center for Education Statistics
http://nces.ed.gov

The National Assessment of Educational Progress (NAEP)
http://nces.ed.gov/nationsreportcard/

NAEP publications by The National Center for Education Statistics: http://nces.ed.gov/pubsearch/getpubcats.asp?sid=031#019

The National Council of Teachers of Mathematics
http://www.nctm.org

Department of Education
http://www.ed.gov/

ERIC Clearinghouse on Assessment and Evaluation
http://ericae.net/

EDPUBS - On line ordering system for Department of Education products
http://www.ed.gov/about/ordering.jsp

The Council of Chief State School Officers
http://www.ccsso.org/

Educational Testing Service
http://www.ets.org/

Indiana University, Bloomington Mathematics Education Program
http://education.indiana.edu/~mathed/

The Center for Research on Learning and Technology at Indiana University, Bloomington
http://www.crlt.indiana.edu