There are several programs who are interested in interviewing IM residents for derm positions. Many are places who are led by double-boarded faculty, as their philosophy in supporting the development of a dually-boarded physician has to trump the economic difficulty of training residents who are quickly using up their federal Medicare funding. It is, however, a rougher road, as you will have a much smaller pool of programs to apply to (my estimate, based on speaking to other successful applicants who completed another residency, is about a 2/3 smaller group of programs).
Go
here for a pdf which outlines the intricacies of Medicare funding and the effect it has on dual residencies.
I must say, it is a beeyatch to apply as an IM resident. First, all the same criteria for stellar applicants apply to you. I could write a whole essay on what needs to be done -- based on actual experiences I have witnessed. (I'll probably throw it into my dermguide.)
So let me start:
You need to get to know a derm department, realistically at your home hospital program. You need letters - both from your IM program director and a dermie at your home hospital. You need to rotate through a derm clinic on your elective time, and impress. You need to do research, again preferably at your home hospital program, and you need to start this your first year if you will apply your second year to avoid a glide year, or your third year if you're willing to chill a year working as a hospitalist. You still need to excel on your IM rotations as a resident because again, you need a good letter from your program director.
And you still need to sleep, survive internship, and find time to do everything above when you are running MICU teams as a second and third year.
Lots of "do's" for the opportunity to apply to a small pool of residencies.
I'd gun for derm as a med student. Waaaay easier.