Ever wanted to sit in on a lecture but didn't want to formally enroll in a college course or couldn't afford tuition? You won't get college credit, but here are some ideas for furthering your education (or just learning for the heck of it).
You might first try searching YouTube, but quickly you'll probably find that it's not easy to get right to the lectures. How about using a site that searches YouTube for you? Apparently Bill Gates Hearts Academic Earth. Academic Earth is a fairly new site that gathers videos from across the Web - including YouTube - and organizes them by subject, by university, and by instructor. You don't have register in order to watch, but if you do create an account you can keep lists of favorites and participate in the site's community, like assigning a grade to each video.
You can also search Google for "free online classes" or something similar. If you're interested in a particular topic, add that to your search words. You might try searching by college or university to see if a certain school offers classes. Look for results that include .edu as part of the domain name. Colleges and universities have their names or initials in their URLs so it's usually pretty easy to identify the right websites. If you're not necessarily interested in college classes, just make sure the websites you do look at are authoritative so you know the information offered is trustworthy.