After reading the stories yesterday about the highest voter turnout since 1968, I did a little more research. It wasn't hard to find a site listing voter turnout (as a percentage of eligible voters) for Presidential elections since 1930. I added 2004 to the table (60% at last count) and turned the whole thing into a simple chart.
You can see that 2004 brings us very close to our highest level of voter turnout in almost a century.
The other notable feature of the chart is the huge drop in 1948, when Harry Truman won reelection in a comeback surprise over Thomas Dewey. I don't know why turnout was so low that year.
Presidential Voter Turnout 1900-2004