I currently a founder and working on a startup at roomplug.com. My company is bootstrap and I was fortunate to hire four amazing talented interns from all around the world (all non-paid and for school credit!). Because of my sound technical background, passion, and able to sell them on my vision, I was able to offer mentorship and guidance to my interns. My previous interns, 1 from Carnegie Mellon, 2 from University of Delft in the Netherlands, and currently one intern, who's working on her PHD, from the University of Kentucky, is working remotely. Usually the internship last from 2-3 months. I'm surprise of the speed in which they work and how amazingly smart my interns were, also to mention I conducted the interview and present some algorithm challenge before I offer them the internships.
If you are looking for some interns, try posting an ad on Internships and Internship Guidance
My advice is, what is it that you are offering your interns? What incentive do they have to work for you over someone else for pay? Sell them on the your vision and perhaps offer them some technical guidance.
On the other note, I could tell who I wanted to be apart of my internship program, they are usually students who are excited of the idea and vision with little to no coercion on my part.
Anyhow, best of luck!