sorry to hear about your situation. i just wanted to let you know that the same thing happened with my husband and i in 2007 except i am the one who went unmatched in derm. the craziest part was that there was 1 derm spot open in the country on scramble day, and it was at the program where my husband matched a categorical residency! what a friggin coincidence. it didn't matter, though, because the derm program did not accept applications and took no one through the scramble.
as for what to do... well, i believe theoretically your husband could have scrambled into a different categorical residency in memphis and gotten out of his prelim spot. at least, this is what my program told me i could do, but i wasn't really interested. anyway, it is too late for that now, and your husband should stick to radiology if that's what he really wants otherwise he will resent you.
i think others have given good advice, and i don't have too much to add, just wanted you to know that you are not alone. this situation is really difficult for a couple (and 2 years later continues to be difficult though i have pretty much come to terms with it).
we really saw three options: 1. i apply for derm and match wherever i can or take whatever out of the match spot i can get then he tries to follow me OR 2. i apply for a different residency altogether and match locally OR 3. my husband completes his residency, i try to get a local derm spot (not realistic), if that doesn't work i reapply for 2011 derm spot. we chose option number 3 because we didn't want to be apart. i think this option is probably easier if it is the female partner who didn't match, because let's face it, not many men's egos would take explaining over and over to everyone that they dind't match but their wife did. in the meantime i am doing research and having a baby. he can't really have a baby so that won't work for him 😉, though i guess you could have a baby and he could take care of it. the option we chose may be a career killer for me, but i guess i am taking my chances. if you guys chose this option, he would only have to sit out 2 years (i am sitting out 3). option #4 would be to be apart, but this was not an option for us. oh, i think there is some sort of acgme rule that you have to complete the last 2 years of your residency in the same program. thus, if he got a spot through the match next year, i am not sure you would be able to follow him to another location since you would only have 1 year left in your residency. you should double check on this.
as far as finding spots outside the match, he should stay in close contact with his program director from his home school. they are generally aware of outside of the match spots that open up (at least they are in derm, i imagine that would be the case for rads as well). also, he could contact nearby programs to see if they have any outside of the match spots.
i wish you the best of luck. this situation is not a good one to be in, and i feel your pain 🙁. always remember to communicate with each other. it is important that you know how he is feeling and vice versa.