Delaware Valley Mensa
Delaware Valley Mensa is the local chapter of Mensa International, the social organization for high-IQ people.
Members score in the top 2% on any of a number of standardized IQ tests - roughly equivalent to an IQ of 133 or above (for comparison, geniuses are generally accepted to have IQs of 160 and above).
The chapter covers from the western suburbs of Philadelphia into Bucks County and down to the tip of the New Jersey Shore. It has around 1,150 members. The monthly bulletin is Proteus.
Each month's chapter meeting (which features a speaker and is generally held in Center City) is open to the public.