As I type this just shy of 95 million votes are in, accounting for 71% of the popular vote. This would put the final count at approximately 133 million once all votes are counted. And that would be a new record. Also worth noting, the spread of the popular vote will be far from the electoral college spread. Clearly this was a brilliantly fought campaign.
Click on the image below for a link to the source, there are important footnotes on the home page.
National Voter Turnout in Federal Elections: 1960–2008
Information Please, Accessed November 5, 2008