...you might be interested in the findings of this report.
It's an evaluation of the Urban Institute's Summer Academy, which for four years has brought minority undergraduates to the Urban Institute for an intensive 8 week summer program. I was privileged to help supervise student research projects for three of these summers.
It's not just a paint-by-numbers exercise (although I think there are a lot of great ideas in the structure of the Urban Institute program itself that are worth borrowing). You need a committed champion for the program: ours couldn't have happened without Lynette and Ashley.