Sign up and participate in your libraries summer reading program! Our library gives out fun little prizes to the kids if they read at least 20 min a day...my kids love the time they get to spend reading plus they get extra excited about the prizes. Young kids can participate too, you just read to them.
If you don't live close to a library you could start your own reading program. We also love making up stories, my little guy loves to have me tell him a story and then he finishes it or sometimes I tell him one and then give him a turn. It's fun to hear his stories!!