I'm a third year, but i notice a lot of 4th years here doing externships...it got me thinking about where i would want to go - is there a website on internal med externships? i think family practice had one on AAFP, but not sure about IM
Most (if not all) sites that have residency programs in internal medicine also offer externships to interested fourth years. Try the frieda website, pick out the programs that interest you the most, and contact the programs directly.
I think it is a great idea to do an externship- you'll see if the place is what you really thought it was, how you like the residents, staff, etc. It is hard to see these things on an interview alone. I worked very hard and the 2 that I did were not easy months but I am so glad I did them.