Although i hate to wade into this muck again, I will say that this issue reminds me a lot of the 9/11 'truth' movement and the 'Bush Lied - People Died' idiocy. Some people will never be satisfied no matter what evidence is produced so it makes no sense to argue with them.
Obama has no incentive to provide any more evidence than he has. The people who matter are satisfied, he is in office and will not be removed, and he has the luxury of being able to point to the nuts who don't believe he is an American citizen as his opponents on major issues.
If you do not agree with Obama's policies (God knows I don't), argue against them on the merits. Do not be seduced by the fantasy that he is not a legitimate president and all it will take is a single document to come to life and it will all be over.