You can make a personal social site for you and your friends. It should include basic PHP and MySQL for login and other simple stuff, making it ideal for learning.
Make it so you can chat and exchange messages with your friends, share links, pictures, videos, etc. You can add a forum and your own blog once you decide to learn even more.
If you manage to make something like that you'll have your own personal simple version of Facebook that you could extend whenever you get more ideas, and best of all you'll have enough skills to try something bigger.
Best of luck.