There has been much written about state constitutions. Below is a list of some of the more recent work:
Mary Whisner, Fifty More Constitutions, 104 Law Libr. J. 331 (2012).
Robert F. Williams, Why State Constitutions Matter, 45 New Eng. L. Rev. 901 (2011).
Symposium, State Constitutionalism in the 21st Century, 115 Penn St. L. Rev. 779 (2011).
William J. Brennan, Jr., What Does--And Does Not--Ail State Constitutional Law, 59 U. Kan. L. Rev. 687 (2011).
Symposium, State Constitutions, 62 Stan. L. Rev. 1513 (2010).
James A. Gardner & Jim Rossi, Foreword: The New Frontier of State Constitutional Law, 46 Wm. & Mary L. Rev. 1231 (2005).
An exhaustive list of references can also be found here:
Montana Department of Public Instruction, A Preliminary Biography on State Constitutions and Education, (1971) OCLC 52864793
The aformentioned Professor Robert F. Williams is Associate Director of the Center for Constitutional Studies, Rutgers University. Information on him and his work can be found here: http://camlaw.rutgers.edu/statecon/frontpage.html
Sanford Levinson, author of Framed: America's 51 Constitutions and the Crisis of Governance, (Oxford University Press) on what we can learn from state constitutions at the national level.