I agree it will vary greatly, but in my experience, undergrad internships can still be fairly varied. I am currently finishing my undergrad clinical/psych practicum and I've been working at a residential treatment facility, helping the staff with their on-campus residential boarding school. I basically do the job of a teaching assistant.
Some of my peers are working in other programs such as pregnancy clinics, men's and women's homes, teen suicide hotlines, hospital psych wards, special education classrooms, and so on.
I would suggest you already be looking into connections to mental health facilities in your area and talking with your supervisor, as once the semester starts, you need to have a placement ASAP.