On December 13, Professor Michael P. McDonald and his United States Elections Project posted data on voter turnout for last month’s election. See here. It shows that Texas had the lowest turnout of any state, although the District of Columbia was even lower than Texas.
If one adds up the vote for the top office on the ballot in each state, in November 2010, one finds only 89,073,836 votes were cast. By contrast, in November 2008, the number of votes cast for President was 131,313,820. Thanks to Thomas Jones for the link.