International Plein Air Painters are organizing a worldwide paint-out for September 5th, 6th and 7th. Check their website to sign up. It's free. And since you'll probably be out painting anyway, it will be nice to know that other plein air painters (in Canada, Belgium, etc) will be participating in the same paint-out. There's also a link to click for purchasing a "Worldwide Paint-Out" t-shirt. Their site is http://www.i-p-a-p.blogspot.com/.
In North Georgia, there will be a paint-out that weekend at the annual "Battle of Tunnel Hill". All plein air painters are invited to attend. For more information, please contact BJ Wright at email@example.com.