This fact sheet from Demos offers talking points that demonstrate the prohibitive cost of voter ID laws to cash-strapped states, the unnecessary burden to election administration, the rarity of in-person impersonation voter fraud, and the disproportionate effects on historically disenfranchised populations.
Demos - Voter Identification Talking Points and Fact Sheet [1]
Links:
[1] http://www.progressivestates.org/sync/pdfs/voterID talking points 011011.pdf
[2] http://www.progressivestates.org/tags/fact-sheet
[3] http://www.progressivestates.org/tags/issue/1785
[4] http://www.progressivestates.org/tags/issue/142
[5] http://www.progressivestates.org/tags/issue/1738
[6] http://www.progressivestates.org/tags/state/1
[7] http://www.progressivestates.org/tags/fighting-voter-id
[8] http://www.progressivestates.org/tags/election-reform