Hmmm... there's three I've had wonderful experiences with.
Vapercon (Richmond VA), Vape Bash (Chicago), and VapeXpo (Ann Arbor MI).
Easily googled if you need more info
Given that you are in Ohio, VapeXpo is this weekend and easily driven to. Vapercon is the oldest, and keeps trading hats for the "biggest" with Vape Bash (Windy City Vaper's Club). VapeXpo is a little more intimate, and has a larger proportion of "locals" than the other "national" meets. Vapercon and Vape Bash are more "tradeshow".
I like all three.