What do you mean?
Way too many candidates to list, in total. Politics1 comes the closest to listing them all. During each and every presidential election cycle, there are, always, people of all political ideologies running for POTUS who are not Democrats or Republicans as well as those who are minor candidates from each major political party. Virgil Goode of the Constitution Party will, probably, get the most “conservative voters not voting for Mitt Romney” votes out of all of the conservative candidates running in ‘12, with Tom Hoefling of America’s Party getting the next total numbers of votes from conservative voters.