Ask HN: How do I get ready for an internship?

I'm looking for a programming internship this summer. I think HN is the right place to ask questions about the process, since many of you work at places I would love to work at. I'm a freshman at UW Madison, but college is not my first exposure to programming; I'm self taught and have been programming for years on my own. I currently work as a web developer (PHP/Rails/JavaScript) for the library at my college's hospital. I'm curious about a few things… 1. Does a college freshman have a shot at an internship with Google, Amazon, or another selective company? It's discouraging to not even have a transcript to send them yet, or any previous experience besides my current job. 2. How should I prepare for an internship at one of those companies? I don't feel like my programming classes are challenging right now. If I want to intern at Google, should I spend more time with C, C++, and Python instead of doing personal projects in Clojure? 3. I've read that if you're looking for a job, a good way to distinguish yourself is to work on open source projects. Is that true for internships too? Does it matter what the project is? 4. What are some other good companies to intern at? Thanks!