Top universities now publish their actual course content online. These are the same lectures, problem sets, and exams used at MIT, Harvard, Stanford, and Berkeley. Used right, they can strengthen your college application and build real skills.
Here's what I've learned: listing courses on your application doesn't impress anyone. What impresses them is what you did with what you learned. One course, done deeply, with a real project at the end, is worth more than ten certificates sitting in a folder.