http://www.ballot-access.org/2008/030108.html#1 http://www.ballot-access.org/2008/030108.html#11Here's the state-by-state registration figures for the states that do them at the link above.
Democrat: 41.66%
Republican: 31.89%
Independent: 24.82%
Reform/Independence Party: 0.42%
Constitution: 0.41%
Green: 0.28%
Libertarian: 0.24%
Other: 0.29%
States with Democrats having largest membership: California, Delaware, D.C., Florida, Kentucky, Louisiana, Maryland, Nevada, New Mexico, New York, North Carolina, Oklahoma, Oregon, Pennsylvania, West Virginia
States with Republicans having largest membership: Arizona, Colorado, Kansas, Nebraska, South Dakota, Wyoming
States with Independents having largest membership: Alaska, Connecticut, Iowa, Maine, Massachusetts, New Hampshire, New Jersey, Rhode Island, Utah