We just did one last weekend: http://cabbqfestival.com/
And our next comp will likely be at Dana Point. All our comps are local here in So Cal. Here's a write up of last years comp (their first ever): http://blogs.ocweekly.com/stickaforkinit/2011/09/dana_point_bbq_championship.php
Not sure if we're doing one before then.
I've done a few, clovisfest in CA and some in Arizona. Best I got was 3rd in ribs and 3rd chicken, 10th brisket and pork out of 50+ competitors.