He was not Muslim at one point. Excuse me for actually quoting wikipedia, but the quote comes from Obama's book:
In The Audacity of Hope, Obama writes that he "was not raised in a religious household." He describes his mother, raised by non-religious parents, as detached from religion, yet "in many ways the most spiritually awakened person that I have ever known." He describes his Kenyan father as "raised a Muslim," but a "confirmed atheist" by the time his parents met, and his Indonesian stepfather as "a man who saw religion as not particularly useful." In the book, Obama explains how, through working with black churches as a community organizer while in his twenties, he came to understand "the power of the African-American religious tradition to spur social change."
I know I'm not going to convince you otherwise (or even to consider voting for him haha) but I would not worry about any ties to the nation of Islam.
My problem with McCain is that he can't stand firm on a policy, and he can't offer solid ideas to move the country forward. He was ready to desert the republicans just a few years ago to become Kerry's running mate. How quickly things like this are forgotten...He hardly seems like a candidate that can diplomatically deal with the world's and our nation's current problems with wars, economic polices, and social policies. I come from a military family (My father was a high ranking officer in the Air Force, I have been involved with the AF, I have numerous cousins/friends still in the Navy and Marines, and my Uncle is still serving in the Army). We have ALWAYS voted republican....but no one is going to this time around, they are actually supporting Obama.
Also, check out this snopes article:
http://www.snopes.com/politics/obama/muslim.asp
Note that it says he was never Muslim.