Ah, back to school season. Even if you’re not actually going back to school, that doesn’t mean you can’t embrace the spirit of the season and ramp up your own personal pursuit of knowledge, especially since these days, you can learn almost anything online!

Online education is one of the biggest trends in Silicon Valley right now and lately, I’ve seen more web-based schools and courses than ever before. They cover all kinds of topics, ranging from Art History to HTML. The best part? Most of these courses are free!

More and more of these education startups are popping up everyday — so much so, in fact, that I’m not sure my own children will ever go to a real college. (Don’t worry, I’ll still buy them awesome pens and backpacks.)

Is online learning the future? Can you get just as good of an education without attending school? Check out the sites below and let us know what you think in the comments below.

1. Khan Academy: This is definitely the place to brush up on that rusty high school calculus and biology. With stand-alone videos and challenges, Khan Academy is a great way to use small intervals of free time to get a refresher course in skills you may not use every day. The courses range from American Civics to Computer Science to Finance — meaning you can achieve a solid foundation in virtually any subject you find yourself a little shaky on. I’m personally using the site to brush up on my Fractions — I always hated those.

2. Coursera: This is most like a college experience because it features actual college professors teaching courses optimized for online learning. The classes are set up much like a regular university class would be: you attend “lecture” at least once a week, take routine assessments, and attend office hours. The one major difference about Coursera and an actual college is that it’s 100% free! (Wish I could have said that about my own college education.) My pick? The upcoming course ‘How to Reason and Argue’ — I’m planning to test my newfound skills out on my husband to see if the course really works ;)

3. Skillshare: This site calls itself a “community marketplace for classes,” and I think that’s fairly accurate. It acts as a hub, helping you find local classes or “hybrid” classes (online classes with local workshops) associated with your interests. You pay-per-course, although some are available for free. If you’re an expert in a specific skill, you can even sign up to teach a course yourself (I’m even thinking about teaching one soon in San Francisco!). There are categories like “Creative Arts,” “Culinary Arts,” and “Entrepreneurship.” I’m pretty sure I want to take them all.

4. Codecademy: Get your code on! This site makes learning to code fun with its simple interface and interactive activities. Even if you’ve never coded before, the lessons will walk you through learning basic coding skills. You can learn basics like Javascript and HTML, or if you’re feeling really adventurous, you can even try a Python class (still in beta)! I have personally used Codecademy and can tell you that this is the only tool out there that doesn’t make coding seem as difficult as hiking Mt. Kilimanjaro.

5. iTunesU: This one’s an oldie but a goodie. If you’re looking to watch or listen to lectures from top universities (yes, including the Ivy schools like Stanford and Harvard) at home or on-the-go, this is an easy way to get unlimited courses at your fingertips. iTunesU also offers “Beyond Campus” classes from organizations like the MoMA (Museum of Modern Art), National Geographic, and more. You can access them anywhere you have access to your iTunes library, making these audio courses perfect for your commute to work or morning run.

6. Course Hero: It’s no secret that the Internet is awesome. You can find virtually any information you need and learn about basically any subject… if you’re willing to sift through all the junk to get there. This site does it for you, compiling courses from articles and videos around the web. The classes are definitely skewed towards the business end of the spectrum, making this a great site for gaining knowledge to help you professionally. If you’re just wanting to brush up on a topic, try checking out their Flashcard section.

7. Udemy: This site offers a wide range of video courses, from practical life skills to high level academic debate. Some of the courses are free and some (including most of the fitness classes) are offered for a fee. There are some classes taught by college professors, some by business professionals, but all by experts in their fields. I’m personally about to start Marissa Mayer’s “New Product Development Process” course. (If you didn’t know, she’s the new CEO of Yahoo! and also serves as an advisor to us here at Brit + Co!)

8. Rosetta Stone: Another classic, Rosetta Stone is most known for teaching foreign language courses, but also offers courses for K-12, higher education, and even business. I’ve taken the Spanish course and can attest that this learning platform is definitely worth the price (so long as you put in the time to practice!). Next up for me? Italian!

9. TED Talks: If you haven’t heard of TED, your world is about to get rocked. The acronym stands for Technology Entertainment Design and is the name of a week-long conference held in southern California that brings together notable thought leaders from each of the three sectors. A selection of the invitees are asked to give a 20-minute talk, some of which are educational, some of which are inspiring, and some of which are just plain interesting. My absolute favorite talk (though I have many) is by Elizabeth Gilbert, the author of Eat Pray Love, and is all about finding your inner creative genius. Sounds suitable for this site, eh?

10. Quora: This question-and-answer site aims to be the knowledge database of the web. I was hesitant about adding it to this list, since it’s quite different from the nine other education resources listed above. Instead of being pushed educational content, you must go and seek it out for yourself. It’s kind of like DIY learning — which is obviously right up our alley here at Brit HQ ;) I’ve learned about so many things from Quora and definitely consider it one of my go-to knowledge hubs. Have you used it before? What have you learned from it?

That rounds it out! Did we miss anything? What’s your favorite online method for expanding your knowledge base? Talk to me in the comments below or over on Twitter.