What areas of interest? And do you mean college classes or just camp themes?
Michigan Tech has a variety of engineering and science themed camps, along with a few business offerings. Prices are somewhat reasonable for sleepover camps. And you could join a few weeks together to make a sampler. However, these are not for college credit. They are also inconveniently located for DMV people to drop off and pick up.
https://www.mtu.edu/syp/
Most of the real summer college programs I've seen are ones where a kid takes just a single college class at the normal price the school charges.