One of the best things about summer is playing a casual game on a field or the beach. In our office, one of our favorite games is called Kubb (rhymes with "tube") that is originally from Sweden. If you have access to some woodworking tools it's pretty easy to make and a lot of fun to play.
What's so fun about the game may not be obvious at first, but after a single game many people get hooked. Trust me, it's worth the bit of effort it takes to make a set. Kubb wiki page Rules of play