Ideas for a 30th Birthday Celebration this Summer?

Photo by PoPville flickr user Caroline Angelo

“Dear PoPville,

My boyfriend is turning 30 on a Sunday this summer and I am trying to come up with some fun, unique ideas for a group of about 20. I would like to do something more exciting than a boozy brunch but not as expensive as chartering a boat on the Potomac for a summer cruise. Any fun ideas??”