What are some cheap things to do for fun?!

What are some cheap things to do for fun?

I am a 22 year old girl who would like to find out what I can do (anywhere) for fun that is cheap. I spend way too much money going out to bars for example on the weekends, and I would love to find alcohol free fun that others could get excited about. I obviously already know the basics like watching tv, movies, playing board games, etc. Any creative ideas?

Hiking.
Volunteering.
Bike riding.
Learning a foreign language.
Napping.
Learning an instrument.
Building something.
Working out.