I'll echo a few other duders's advice to avoid unpaid internships if you can.
I interned as a billing assistant for an engineering consultant firm (mostly reviewing pre-invoices with construction project managers, data management, some admin stuff like copying, filing, and reporting) right after I graduated from college. They liked me so much they hired me at the end of my internship. I'm still working at the same place though I am looking around for a new job.
Good luck at your internship!