Ballot Access News reports

This year, 23 presidential candidates are on the ballot in at least one state. That is the highest in U.S. history except for 1992, when there were also 23. Generally there are more such candidates in periods of great public unhappiness.

Here is a list, with the predominant party label for each, and the percentage of the voters that will see their names on the ballot:

Barack Obama, Democratic, 100.0%
John McCain, Republican, 100.0%
Bob Barr, Libertarian, 94.5%
Ralph Nader, independent, 85.2%
Cynthia McKinney, Green, 70.5%
Chuck Baldwin, Constitution, 59.8%
Gloria La Riva, Socialism and Liberation, 26.8%
Roger Calero or his stand-in James Harris, Socialist Workers, 25.0%
Brian Moore, Socialist, 21.5%
Alan Keyes, America’s Independent Party, 18.1%
Charles Jay, Boston Tea, 10.0%
Gene Amondson, Prohibition, 9.6%
Thomas Robert Stevens, Objectivist, 8.0%
Richard Duncan, independent, 4.6%
John Joseph Polachek, New, 4.3%
Jeffrey Boss, Vote Here, 3.0%
Jeffrey Wamboldt, We the People, 2.5%
Ron Paul, Taxpayers/Constitution, 2.0%
Jonathan E.