We all know that the internet is full of ways to waste time. From adorable animal pictures, to silly gifs and yet another scroll through social media, our online lives can sometimes feel like one useless (if stress relieving) time suck.

But there's no need to spend the majority of your time on the internet numbing your brain rather than feeding it. If you'd like to learn basically anything, there's a website that can help you do it simply -- and probably for free.

Not sure where to get started? Kristyna Zapletalova, founder and CEO of startup Maqtoob, can help. On Medium recently she rounded up an impressive 37 websites that let you learn new skills and get smarter. Some, like Coursera and Code.org, have been extensively covered elsewhere and so have probably crossed your radar already, but others may be new to you, including

Dash--Learn to make awesome websites. DataQuest--Learn data science in your browser. Lingvist--Learn a language in 200 hours. [I'm skeptical about the 200 hours claim. Has anyone tried it and succeeded?] Thinkful--Advance your career with 1-on-1 mentorship. Platzi--Live streaming classes on design, marketing, and code. Highbrow--Get bite-size daily courses to your inbox. Memrise--Use flashcards to learn vocabulary. [Note: The site's co-founder recently shared memory tips here on Inc.com] Learnist--Learn from expertly curated web, print, and video content. Chesscademy--Learn how to play chess for free. Pianu--A new way to learn piano online, interactively. Yousician-- Your personal guitar tutor for the digital age. CreativeLive--Take free creative classes from the world's top experts.

Still haven't found anything that strikes your fancy? Check out the complete Medium post for a lot more ideas.

But be warned, once you've seen this list, you have absolutely no excuse for an online diet consisting entirely of cute kittens and entertaining YouTube videos. Isn't it about time you devote some of your browsing time to learning something new?