I haven't had one up to this point, and I'm not an absolute rockstar coder, and I feel like these two things are making me easily fall through the cracks with some of the bigger companies I've interviewed with.
What's your best advice, whether you're a recruiter or have been in my position, for somebody trying to score a good internship?
Although I'm only a freshmen in college, I've already held three internships (I started interning during junior year of high school). I even have one set up for next semester, and have a few offers for the summer. The thing that sets me apart from other candidates is my passion and willingness to set aside time to work on projects outside of class.
The first year that I started programming I made a blackberry app on my own for fun (it was terrible and barely functioned, but it was something cool and something that I enjoyed making). I soon moved on to Android and programmed a few "service applications" for my high school (nothing huge, but something that definitely set me apart and again something I really enjoyed and love to talk about). During interviews, it's these side projects that I like to talk about and not what I worked on during the time I was interning.
Another important thing is to not give up and to never stop learning on your own. The only way to be a rockstar coder is through practice. Take the time to work on something cool, even if it has been done before, try to figure out how to make it yourself with minimal help.
As a bit of personal advice, I've worked in a complex corporate environment, a terrible start-up environment, and a wonderful start-up environment. It is important to remember that even after you get an internship offer the struggle doesn't end there. It is also important to remember that an internship is only limited to what you make out of it, there are no such things as a "good" or "bad" internship.