In our biased opinion, Mensa is the best high-IQ society. But, in fairness, here are links to other high-IQ sites. These open in a new browser window.

Intertel
Requiring a score at or above the 99th percentile

High-IQ Links Galore
Just a ton of links to tests and other societies

ISPE
The International Society for Philosophical Enquiry. Must score at the 99.9th percentile.

Poetic Genius Society
Must score at the 99.5th percentile and have a passion for poetry.

Hells Ms
The Mensa Party SIG (Special Interest Group) These people love to have fun!

Region 3 Mensa
ECOM's just one local group within this region.

Cincinnati Area Mensa
Cleveland Area Mensa
Columbus Area Mensa
Dayton Area Mensa
Maumee Valley Mensa (Toledo OH)
Blue Grass Mensa (Lexington, KY)
Mid-Michigan Mensa (Lansing, MI)
Northern Michigan Mensa (Traverse City, MI)
Vandalia Mensa (Charleston WV)
Rochester Area Mensa (Rochester, NY)
Southeast Michigan Mensa (Detroit MI)
Western Michigan Mensa (Grand Rapids, MI)
Western New York Mensa (Buffalo, NY)
Western Pa. Mensa - A Support Group for the Severely Gifted (Pittsburgh PA)
Kentuckiana Mensa (Louisville, KY)

American Mensa
The National-level site

Mensa International
Yep, you guessed it, the International-level site

Canadian Mensa
Need we explain?

Mensa Process - Putting Brilliance to Work
A global consulting firm - "Think of us as your private brain trust - a group of exceptionally intelligent, highly creative people dedicated to helping your organization address its most vexing challenges. Drawing on the unique abilities of Mensa members around the globe, we provide novel input and breakthrough thinking on the issues you face today - and the challenges you'll face tomorrow."

Crendel.com's web directory page for High Intelligence organizations has a number of links you may find interesting, too.