Many people believe you can't have fun without alcohol. Sure, it may be funny to watch drunk people try to walk and talk, however, it won't be so fun the next morning when they wake up with a hangover and don't remember what happened the night before. It is possible to have fun without drinking; trust me, I do it all the time.
Get a group of friends together and do something everyone would like. You can go hiking, go whitewater rafting, or anything outdoors. My school has sand volleyball tournaments and paint parties; we find ways to have fun (even though you might have to take a shower when you are done). When it is cold outside, get a group together to go and do the cold water challenge and jump in a lake. It will be cold as all get out, but it will be so much fun. You can do crazy things without drinking; it may mean more common sense, but you can still have fun. When you find things that are fun for you, alcohol isn't even thought of. You will make memories while seeing amazing views. When you get into nature with friends, you learn things about them that you never knew before and you wouldn't have found out any other way.
People can get together and play board games. Games like that can be very entertaining. At my school, we get a group of people to play Rule of Signs. You come up with your own sign and you throw an imaginary ball around using your sign; the person in the middle is trying to figure out who has the ball. You have to be open to doing things that you think are childish. Most of the time you will end up having fun!
If you like singing, you can get people together who play guitar (or other portable instruments) and have a small jam session. You can make up songs that you wish you could hear on the radio, or just gibberish to be funny. Whatever you want to do that would be fun, just do it. I promise it will be more fun without alcohol or drugs.
My school is a dry campus, meaning nobody on campus (whether you are of age or not) can have alcohol on campus. We have so much fun all the time. We have bonfires, cookouts, paint parties, dances, Halloween parties, etc. We never have alcohol, but every person has fun. I don't see the pull to have alcohol; I don't care about having it. I have gone to a party before where there was alcohol and I didn't have anywhere near as much fun as I do when I'm at one that doesn't have any alcohol. So, skip the alcohol and have more fun than the people drinking.