For those around or close to the Mid-Hudson Valley, NY. The Saugerties garlic festival is the last weekend of September. I go every year to get my garlic to plant and also last me through the winter. Small town but ALOT of people show up. I'd advise going early if you're goin'.
They have craft venders, shows for the kids, cooking demo's, food everywhere, and a TON of garlic vendors.
Here's a url if you wanna check it out. It's five bucks at the gate (that's good for both days, I think). And no, I'm not affiliated with them in any way what so ever. (well, 'cept I love garlic! ;-) )