The Census Bureau has released “Voting and Registration in the Election of November 2010”. The report can be seen at this link. The Census Bureau has been preparing this report for many decades. A new report is released after each Congressional election. The data is from surveys, not from election returns statistics.
Oregon, Washington, and Maine, have the highest participation. Oregon and Washington are the only two states that send ballots in the postal mail to all registered voters (although in 2010, Washington state had one county that didn’t do that). And Maine, in 2010, was one of the states with election day registration. Ironically, the Maine legislature repealed provision for election-day registration this year, but that change isn’t in effect because a referendum petition was filed to let voters vote on election-day registration in November 2012.