Everyone knows celebrity endorsements sell everything from zit cream to Cambell's soup. This election season, celebrity endorsements are also selling policy. Heres a break down of some of the big names plugging for Barack Obama and John McCain.       John McCain: EntertainmentStephen Baldwin, actorJerry Bruckheimer, producerClint Eastwood, actor and directorKelsey Grammer, actor Dennis Miller, comedianKevin Sorbo, actorTom Selleck, actorSylvester Stallone, actorRip Torn, actorJon Voight, actor Adam Carolla, comedian, television and radio host AthletesTroy...