There are a number of references regarding the false statements about Obama's so-called "Muslim ties", his refusal to place his hand over his heart during the Pledge of Allegiance and many other untruths that have been forwarded ad nauseum for the past six months or so. Snopes has several different links regarding the same, but this one is quite detailed and factual.
http://www.snopes.com/politics/obama/muslim.asp
I think it's interesting that of all the candidates, every single one who has shortcomings and history they're probably not proud of, more people focus on Obama than any of the others. I chalk it up to the fact that he's black and has a name that offends some. There's certainly no other good reason for such a never-ending deluge of out-and-out slander.
-nab