I hope that Barack Obama will be the next president. He's the only presidential candidate that has run for office in my lifetime whom I genuinely admire, although I am a bit of a cynic when it comes to modern politicians. It may seem a rather shallow reason for voting for him, but I love his story and the idealism that his ascendency to the presidency would affirm. I truly believe him to be a man of integrity and think his example (were he to win) would lead many American politicians to reflect on their methods and messages. I wouldn't expect a lot of practical day-to-day changes, but think that his success could inspire a lot of reluctant but well-meaning people to reconsider running for elected office knowing that it is possible to win without selling your soul.
Also, I just really don't want either of the other two candidates to become president. I do admire John McCain a lot for being a maverick. He too seems to be a man of principle, but he's also a hot-head and many of his foreign policy positions scare me. As for Hillary... well, I just don't like her. While her political positions are very similar to Obama's, she represents almost the exact opposite of everything he does. She's deceitful, manipulative, hypocritical, and (at least in elections) rather machiavellian. She'll do anything to get elected, and has hurt the image of the Democratic Party with her tactics against Obama. In end though, I not only hope but expect that Barack Obama will be the next president. Despite the wrangling I expect to see from the Clinton camp every step of the way, Obama is almost surely going to be the Democratic nominee, and it would take a miracle for the Republicans to win the election this year.