There's tons of opportunities from summer grants from you school, global health grants, minority grants, specialty grants, aoa, NIH, medical/surgical societies, and other universities.
Ask one of your deans about this when you get there and they will have all the resources laid out for you. My school has a webpage listing every fellowship grant opportunity.
Bottom line, there's tons of programs/money. Just start early because for many deadlines are Dec/Jan the year before you leave. I remember I started my process in October of MS1.