Where Y'at magazine is giving away a pair of 3 day passes to Voodoo (closed now), and Live Music Blog is also giving away a pair of 3 day passes, along with a meet & greet with Moon Taxi and stage passes for their set.
Update (09/17/13): Here's another chance to win tickets...from Voodoo on Facebook - "Build your Voodoo path and you could win a pair of weekend credentials for the ritual! Create your Voodoo schedule, share on your Facebook and Twitter pages, and you'll be automatically entered to win. To build your Voodoo path: http://goo.gl/WJtxyw"
Update (09/24/13): Consequence of Sound is giving away VIP passes and hotel accommodations. Enter to win here, which should also help give me more entries to win. :)
Also, the Voodoo ticket office is claiming they will not be selling single day passes this year, only 3 day. I don't buy this for a second! They might wait until the week of the show, or even day of the show, but they will have single day passes available somewhere. I would stake my life on that. But you should know that this is what they are telling people over the phone, so that's the official position as of now.