Samer Hamadeh, Co-author of The Internship Bible and America’s Top Internships. Former Vault.com CEO.
You can apply for some internships while you're in high school, but for most internships, the pre-requisite is that you are a current college student. Definitely check out the internships on Noodle and read the requirements carefully. That said, even if you're not in college, consider applying anyway, especially to a local business that hasn't posted an internship anywhere and especially if you possess a special talent (eg, iOS programmer or graphic designer) that doesn't necessarily require college enrollment or a college degree. Companies are salivating for talent, not credentials.