Don't forget to keep math alive this summer with your summer math calendars and other math talk!
Estimate the cost of things ---- gas, ice cream, sun screen :)
Try to estimate the amount of time it will take for you to get complete soaked running through a sprinkler!
Are you going on a trip? Estimate the amount of time it will take to get there, keep track of the actual time, and compute the difference - how did you do?
Most of all have fun! Just don't forget about math!