GO DOWNTOWN. Walk downtown and look at stuff. If your downtown has a mini little splash thing, get wet there instead of spending money on going to a waterpark and having to pay for gas and get snacks when you're on your way down there.
MEET UP WITH YOUR FRIENDS. Go to the mall and walk around with your friends. If you have a local park and they have movie nights, outside go there. Go bike riding around your neighborhood.
DECORATE. Decorate your room. Ask your parents to paint your room, hang up pictures, put lights up, move your bed around and tv.
EXERCISE. Go walk somewhere. You know if you want to wear a two piece, do some walking so you can fit exactly in it.
SPORTS. Do a mini sport outside your yard so you can stay active for the summer. So you won't be one of those lazy people that don't like to do anything.