At long last, the semester is over and celebrations have begun. Most of us are already relaxing at home or somewhere sunny by now, a well-deserved break after a long week of exams and papers, and an even longer semester. While this mindless paradise might be nice right now, eventually there will probably be a point in the summer where you realize you need some mental stimulation before you enter full on zombie-mode. Fortunately, the Internet has blessed us with countless resources to keep our minds fresh, and it only takes a few minutes each day to avoid becoming a vegetable. This is by no means a complete list, only the most popular free resources for self-education (here are two more comprehensive lists).

Duolingo

While you won’t become fluent by only using Duolingo, it’s a wonderful website that guides you through the basics. 10 minutes a day is enough to give you a decent foundation in a language, and the exercises are strangely addicting. It’s also a solid way to review a language you might not practice anymore, or at the very least, help you retain some vocab over the summer.

Memrise

This flashcard-based app is designed for learning languages, offering much more variety than Duolingo, but less grammar and structure. Rote memorization isn’t a bad place to start, though, so it’s certainly got its uses. There are hundreds of sets of flashcards on every subject, though, including some random trivia sets that would only ever be useful if you make it on Jeopardy.

Quizlet

Another flashcard app, this one ups the ante with matching games! This is great if you’re like me and have the attention span of a 6-year-old and need some matching games to break up your regular flashcards. Quizlet seems to emphasize making your own flashcards, but you can also bookmark and use other people’s flashcards, too.

Khan Academy

This is my go-to for faking productivity—I can watch Khan Academy videos with minimal brain-power required, but I feel like I’m absorbing information. A lot of the videos are at a high school or intro college level, but the articles are in-depth enough to still be relevant. And when stuff gets complicated, a simpler explanation is actually a million times more helpful than all the details anyway. If nothing else, it’s a good way to review things you already know and explore things you haven’t learned yet.

Mango Languages

Another language learning program, this one is the most structured. In addition to just learning the language, Mango offers tidbits of information about the culture, as well as paragraphs about the grammar of the language every so often. This program feels a lot more academic, and its highly repetitive structure drills vocab and pronunciations, in addition to providing realistic examples of conversation and listening exercises.

MIT Open Courseware

Dozens of universities offer free class materials on their own open courseware sites, but the MIT Open Courseware is one of the more popular ones, probably because of the push for STEM-skills regardless of career field. Open Courseware gives you free access to hundreds of university courses, which you can work through at your own pace.

TED Talks

This is another vast resource of videos you can watch with minimal input and still feel like you’ve gained something. TED Talks cover just about every subject you could possibly be interested in, so there’s bound to be something worth watching. With videos as short as four minutes, you’re guaranteed to be able to fit a TED Talk into any window of free time you might have and learn something new.

Fluent In 3 Months

While this website won’t directly teach you anything, the blog posts and discussion forums have countless links to external resources with tried and true language learning tips. It’s also highly motivating to see what other people are learning, and it can be a great support community if you get involved with the forums. Conveniently enough, there are three months of summer break, and if you’re truly dedicated, you can come back in August with a new language to impress your classmates with.

Project Gutenberg

If you’re anything like me, your summer plans include quite a bit of reading, and where else to get your classic literature than a free database of old books? Project Gutenberg. High school teachers swear by it, and I used to think they were crazy, but it’s actually a great place to look for online copies of anything old enough to not be copyrighted anymore.

PBS’ NOVA

This might be one of my favorite educational resources only because they talk about space a lot. You literally can’t go wrong with Neil deGrasse Tyson or astronomy, but NOVA covers everything from history to biology to math. When you need a break from your regular Netflix binge-session, watch an episode or two of NOVA to jumpstart your brain.

Netflix

There’s an entire category of documentaries and educational videos here, so I’m sure you can find something you’re interested in. I am a huge nerd and absolutely adore David Attenborough’s series, including "Blue Planet," "Planet Earth" and "Life," all of which can be found on Netflix. Whether half-hour episodes in a series or a two-hour stand-alone documentary, you can learn about literally anything with as much or as little engagement as you want. Even if you let documentaries play in the background while you multitask, you’ll probably pick up a few new facts to impress your friends with.