After a difficult school year, the last thing that you're probably thinking of is how you can be productive over the summer. But summer break is usually three months long and you are almost guaranteed to be bored at some point. Here are a few ways that you can keep yourself sane during those moments.
Taking summer classes
Ahh. So you've had a difficult academic year but you just can't get enough of classes. This is a good idea if you're behind on your graduation timeline. It's also a good strategy if you aren't able to fit the class in your fall/winter semester or need it as a prerequisite for a class that you will be taking. This would also work well if you want to lighten your class load during the school year.
The main disadvantage is that they can get expensive. You also get little financial aid over the summer because it's factored in with your fall and winter semesters. Basically, any unused financial aid gets rolled over to the summer and most people accept their full award, leaving nothing for the spring/summer. Many people opt to take courses at their community college, but if you're applying to a professional school (law, medical, physical therapy, etc) then you will need to consider how it will look on your application.
Getting relevant work experience
The summer is a time to explore and experiment around. Getting a job over the summer helps pay for college and getting a job or internship in an area that pertains to your field would be the ideal situation. Even if there's an unpaid position open, you should still go for it because there's much you can learn no matter where you go. The advantage of this is that you will have a better idea of what you want to do in the future.
Doing research
The summer is also a time to literally experiment around. You'll be able to put more time into your research projects that you didn't have during the school year.
Ask almost any professor and they will tell you about their research. It's not just the hard science professors who do research; pretty much all professors in their fields do research. This is good to get involved in if you are curious as to what their field is like today.
Reading
Reading is underrated. There is much you can learn from picking up a book. Reading a fiction book is productive because it stimulates the imagination. Nonfiction is also good for obvious reasons. Numerous opportunities to learn await you and you just need to make that first move of checking out or ordering the book. This is also one of the simplest ways to pick up on skills.