In an appeal to the Republican Party's conservative base, John McCain said that he does not support the law that legalized abortion and that it should be overturned. This contradicts his statements on the campaign trail in 1999 when he took a softer stance, saying that he "would not support repeal of Roe vs. Wade, which would then force x number of women in America to [undergo] illegal and dangerous operations."
While in South Carolina, he also attended an abstinence-only rally for students, sponsored by a crisis pregnancy center (whose website compares the link between abortion & breast cancer with the link between smoking & cancer—a new twist on an old myth).
According to a recent poll, McCain is out of sync with over 60% of Americans who would not like to see Roe v. Wade overturned.
Also, check out E.J. Dionne Jr.'s terrific op-ed column in The Washington Post on abortion as a political litmus test for hypocrisy.
As for the democratic candidates, Daily Kos has a story on their positions (broken down by issue).