UCD does.
Historically University of Kansas, Cleveland Clinic, University of Pennsylvania, though worthwhile to review with the UCD medical faculty office for additions/subtractions to that list.
These are universities with a presetup elective for UCD students to go to during a summertime. For Kansas/Penn, med students sent in a form of some sort and it was selected who went. Not exceptionally competitive though, since most med students would just bypass UCD's presetup electives and arrange their own electives in the discipline and school or state/province in which they wanted to do residency. There is only a fixed amount of time to do electives since need to have clinical years under belt for most things, and thus want to focus on what electives will both help you learn about a discipline and program and also let that program kick your tires before hiring you.
Peace out.