Recently, for her 65th birthday, my aunt went hot air ballooning. She said it was pretty amazing, with the breathtaking views and the exhilarating rush of adrenaline making it her best birthday in some time.
I definitely want to try hot air ballooning at some point (hopefully before I am 65!), but until then I think going to one of the ballooning festivals would be very fun. If nothing else, it would provide for some incredibly cool photographs.
HotAirBalloon.com has a comprehensive list of ballooning events and festivals.......there is bound to be one near you!