Daniel (author of Formerly Barred) has posted something I've been mulling over and hadn't yet bothered to collect quotes for aside from one or two. I think I'll save myself the trouble and simply link to his post. Whether or not you believe the current political battle over same-sex marriage can or should be compared to the doctrine of plural marriage, the statements of past prophets certainly offer some food for thought.
Incidentally, to my knowledge, such statements have never been officially retracted or denounced by any presidents of the church since. As far as I can tell, those statements are a reflection of LDS doctrine, and plural marriage is still considered a celestial order despite being forbidden in modern institutional practice. Even though I strongly dislike the idea of practicing it (hey, back off--I struggle enough with the idea of one wife, OK?), I think it should be legal (that doesn't mean making child abuse and tax evasion legal, folks).
I'm not sure why people keep quoting the church as saying "one man and one woman," but I've not seen them use such wording. They've said "a man and a woman." That may seem like splitting hairs, but I don't believe the church authorities chose that wording lightly. I'd guess they dare not totally close the door on the future of plural marriage. They're clever that way.
On a related note, I've often wondered whether legalization of same-sex marriage will ironically open the door for the legalization of plural marriage, which will then open the door for another revelation reinstating the practice within the church (probably only when it happens on a global scale)? After all, might it not be hypocritical for supporters of non-traditional marriages who claim to support "all" families if they were to reject a non-traditional but historically very traditional form of family? You get ready for it. It'll happen. I prophesy. *hiding under the table to avoid lightning strikes...because it's storming outside...why else?*