The Dayton Hamvention used to (and may still) be the worlds largest gathering of radio amateur enthusiasts.
More info at: http://www.hamvention.org/
It's also great place to pick up used test equipment and components. I have not missed one in decades. I have a couple of spaces out in the parking lot with some friends, and we sell mostly junk, and occasionally big lasers.
We have booth spaces #3822 & 3823 - Anyone showing an Adafruit Skill Badge will have access to our cooler and junk food box (while supplies last).
Sunscreen given to all comers.
Prices on some items vary with weather, and drop as time goes by. Sunday about 10:00, is a great time to check out the trash piles, and folks leave the 'fest
Here we are trying to cram a ruby pulse laser into a car.. http://www.youtube.com/watch?v=CgMLXWsS2ms