As I understand it, the only rights that marriage guarantees are those to tax exemptions (but beware of marriage penalty!) and social security benefits. Everything else is conditional e.g. you may be entitled to benefits offered by your partner's employer if such benefits are provided, but the fact of the matter is that many companies (such as Johns Hopkins) already provide benefits to domestic partners of the same sex (different sex partners need marriage license, though). Moreover, if your employer provide benefits to employees only, or do not provide them at all, the "rights" of homosexuals and heterosexuals are exactly the same - the right to nothing.
Common property - this depends whether the state is a "community property state" and most states in the Union are not. MD is, PA is not. As a result, my PA wife has the right to 50% of my MD assets earned since marriage, but I have the right to 0% of her assets hidden in the vast wastelands of PA :). Therefore, my rights in PA in this respect are not much those different than those of same sex partners.
Children or rather adoption thereof (obviously) - heterosexual marriage does not guarantee any rights to adoption, singles can adopt and that puts them on equal footing with same sex partners (who are legally single).
I do not think there is a "right" to sexual favors for anyone, married or not (there is, after all, such a thing as marital rape).
I am not quite sure what other rights you have in mind.
Wojtek