UPDATE: One of my kids' favorite summer activities is picking grapes from the fridge, putting them in a cup and waiting for them to freeze. (Then they eat them.) Go figure. I also froze half bananas on popsicle sticks and my kids LOVED them.
Bananas and strawberries make great shakes, "ice cream," and ice pops. (I add yogurt and milk for pops.) Ice pops can also be stored in a zip-top bag or container after they are solid.
Also see my post on Adult-Worthy Ice Pops.