If you've wanted to boost your learning or have something nice on your college application, you should look into taking an online course.
Online courses are courses provided by universities, sometimes for free, that you can take online and sometimes get an official certificate for completing. Of course, this means you have to dedicate time to it. If you're interested, here are some websites where you can find some online courses.
Coursera is one of the biggest online course websites out there. Simply sign up for an account, and you're already there. If you want to learn web design, just search for web design. If you want to learn English, just search English. As an example, I took the Grammar and Punctuation course from the University of Irvine, California.
While most of the classes are free, free classes do not provide you with an official certificate, you have to pay to get those. However, you can still learn useful skills from high-ranking universities for free. Most of them are only a few weeks long, so you won't have to take much time out of your day to do them.
Springboard is a website that provides student advisors and mentors for you to advance your learning. While the course choices are much more limited (they only provide a few workshops at a time), they're very detailed and they help you set up your portfolio by giving you projects. Creating a portfolio for what you've done will look impressive to many universities. Springboard is a more detailed and hands-on website than Coursera, and will look impressive on a resumé.
Open2Study is an online learning site that provides short lessons in specialised areas, like nutrition and leadership. Just like Coursera, you can take any amount of free courses you want, but to get accredited, you have to pay. However, many of the courses are self paced, unlike Coursera, so you can learn without any deadlines.
edX is an online course website, just like the previous three, but its more focused on information technology courses, just like Springboard. You can learn things like design, programming, and project management from highly established universities like Harvard, MIT, and Berkeley. While you do have to pay, having a certificate from an Ivy League school will certainly make your resume look better.