You can grow strawberries at home, of course, but it's also fun to visit a pick-your-own farm.
PickYourOwn.org has a wonderful site full of listings of pick-your-own and cut-your-own farms all over the U.S. The listings are searchable, listed by state, and they have many great tips for picking techniques on the site as well. So find a farm in your area and enjoy the company of other pickers.
Once you have your fruit picked and home, be sure to wash it and then have fun making some strawberry shortcake.
If you want a little more variety, try some of these strawberry recipes.
Picking berries isn't free, but it's a pretty inexpensive way to spend a summer day. Check out these ideas for free or inexpensive summer activities:
Top 10 Free Summer Ideas
Free Activities in Your Hometown
Frugal Fourth of July