uhhhh, pretty much EVERY scholarship falls into at least one of those categories. If you find a scholarship that doesnt fall into the low income one, PM me because I would like one, but have yet to find one. I think there are quite a few minority scholarships out there as well.
This is another way med school is different from undergrad, there's just not a whole bunch of scholarships outside of what you'll find your in your school's financial aid office (my school offers like 30 minority/low income scholarships for every 1 academic/acheivement scholarship). So check with your school; if you don't qualify or are offered institutional aid, you'll probably have to go with Stafford loans like us lower middle class Caucasians.
Most of the scholarships will be rewarded to you without you having to do anything other than fill out the normal paperwork for your med school. They will determine what you qualify for. As for outside scholarships, UNCF does have some but there really arent many outside scholarships that I could find during my search before first year.