Thought I'd chime in with my views on gay marriage. In short, I'm all for it. But in order to elaborate, I must draw a sharp distinction between the religious and civil aspects of a marriage.
A marriage ceremony performed in a church or by a representative of a church should thus be considered a religious ceremony. In that sense, a church has the right to approve or forbid same-sex marriage between members of their flock based on that church's particular dogma. Under the Separation of Church and State, Congress cannot pass any laws - nor can any proposition be voted upon - to grant or deny any rights or restrictions on a religious ceremony, nor is any religious union between two people legally binding in the secular world.
One isn't granted any civil protections or legal rights from a Baptism, Confirmation, Bris, Bar or Bat Mitvah, so why should (church) marriage be any different? The granting of any such entitlements on the basis of a religious ceremony - joint filing of tax returns, property/inheritance rights, medical insurance or any of the thousands of earthly benefits traditionally connected with marriage - is constitutionally indefensible.
On the other hand...
A marriage ceremony performed by a Justice of the Peace, Notary Public, Ship Captain, or any such layperson with the power vested in them by a civil authority, is a legally binding civil union and as such - be they M/F, M/M, or F/F - ought to be entitled to all the same legal rights, privileges and protections historically reserved for M/F couples. It is up to lawmakers (not the voting public, incidentally) to decide how these issues are to be legislated.
Couples with religious beliefs would then have two ceremonies, one in which their immortal souls are united in the eyes of God, and another where their mortal bodies are united in the eyes of civil institutions.
People opposed to same-sex (civil) marriage need to remove their religious dogmas from the equation. Traditional family values are not being threatened. The gays are not coming to bust up your marriage. To suggest otherwise is to suggest that the only reason that your husband married you instead of his fishing buddy is either fear of the wrath of God or the limit of the law.