Gwen Helfrich has an program on Chicago Public Radio called Odyssey, and she has a show in her archives featuring two legal scholars (Andrew Koppelman and Cass Sunstein) that focusses on the purely legal technicalities that would come into play if a constitutional amendment didn't pass, and in the future some states allowed gay marriage and other states didn't. I found it interesting not only as a review of the relevant marriage law (interracial, polygamy, underage, etc.) but even more as a defense from a liberal perspective of the U.S. federalist system as a set of coherent principles, rather than just as a mixture of bad faith and historical compromises we've just been stuck with.
The show is available on realaudio at: http://www.wbez.org/audio_library/ram_2004/odyssey/od_040226.ram
Michael