Legally, unpaid interns aren't allowed to do anything but unproductive work, though, like getting coffee. They cannot do anything that paid employees do for that employer. If they do then they have to get paid.
If course this is usually only followed never.
Edit: I shouldn't say that so matter-of-factly, but that's my recollection from previous information. I'm sure it varies by state as well.
Edit the second: Here's what the department of labor says:
- The internship is similar to training that would be given in an educational environment.
- The internship experience is for the benefit of the intern.
- The intern doesn't displace regular employees and works under close supervision of existing staff.
- The employer doesn't gain an immediate advantage from the intern's activities—and on occasion the employer's operations may be impeded by the intern's activities.
- The intern isn't guaranteed a job at the end of the program.
- The employer and the intern each understand that the internship is unpaid.