Map of the US showing states that permit no-excuse early voting.
Current as of September, 2014.

  States with both in-person and postal no-excuse early voting.
  States with only in-person no-excuse early voting.
  States with only postal no-excuse voting.
  States without no-excuse early voting.
Vector map from Blank US Map.svg by User:Theshibboleth.
Colors from Map-of-US-state-cannabis-laws.png by CL8.
Updated 2014 from Absentee and Early Voting. National Conference of State Legislatures.More sources:

http://ballotpedia.org/Early_voting
http://www.longdistancevoter.org/early_voting_calendar
J. Winton - author of first upload here.