What says “summer is here” more than the nice weather? It’s the flood of eager college kids who are keen to get hired for a few months to get some real commercial development experience.
The challenge for employers is in the interview process. Because the candidates are both young and inexperienced, it can be tough to gauge the skill level of somebody so “green”. Assuming they are being hired to actually write code, you should of course check their knowledge of fundamental algorithms and data structures. However that might not whittle down the list enough, so how can you figure out which of these fresh-faced kids are the best of the bunch?
Ask them two extra questions:
When did you start programming?
If they answer, “For my assignments in CS101”, put them at the bottom of the pile.
If they instead answer, “When I was 13, I started creating my own web pages and coding Javascript utilities to make them do more cool stuff, and I haven’t looked back since”, put them at top of the stack.
Do you write software in your spare time?
If they answer, “Yes, I just built this iPhone app to see if I could, and now I’m writing a Sudoko app for Android for fun”, well, you guessed it: top of the stack.
The answers to these simple questions tell you if the candidate chose to study computer science because it sounded like a good career choice, or if software was already their passion. And that can make the difference between a good internship and an awesome one.
More Than Coding 
Some of the best engineers I know took a programming class in college and got started there.