The celebration was held at the Lake of the Ozarks (LotO) in the summer of 2008.
http://www.youtube.com/watch?v=WD_eYnmexAs
Below are some links to various photos:
PICTURES of our "50 Years of Spridgets" gathering of Presidents at Lake of the Ozarks!!
Presidents Johnson & Altman Pictures
President Gryf Ketcherside's Pictures
President Glen Byrns' Pictures