Source: Keesha Gaskins and Sundeep Iyer, Brennan Center for Justice at New York University School of Law, 2012

From the summary:
Ten states now have unprecedented restrictive voter ID laws. Alabama, Georgia, Indiana, Kansas, Mississippi, Pennsylvania, South Carolina, Tennessee, Texas, and Wisconsin all require citizens to produce specific types of government-issued photo identification before they can cast a vote that will count. Legal precedent requires these states to provide free photo ID to eligible voters who do not have one. Unfortunately, these free IDs are not equally accessible to all voters. This report is the first comprehensive assessment of the difficulties that eligible voters face in obtaining free photo ID.
See also:
– Executive Summary
– Foreword by Michael Waldman
– See Voter ID Maps

The Challenge of Obtaining Voter Identification