Parks
You can find some cool parks out there that you can go to for free and have fun all day at. You can have a picnic, fly a kite, play baseball, or just layout and get that nice tan you are looking for and it's all free.
Go swimming
There are lots of place you can go and get wet for free. You can go to the river and go tubing, swim, fish, and boating. You can a pond and do the same things and it can be all free fun. You could even go the beach if you live near one. Water can be all day free fun.
Go for a hike
Getting out a taking a hike can be lots of fun and it's good for you too. You can take a packed lunch and have out in the wood. You can make it a two day trip to camp out too. You can have all this fun and it's all free too. In this hard time free sounds like a good thing to do.