I would like to get tickets to the Burning Man festival, Where can I find ticket for it? It seems they are sold out months ago.
For 2012, it would seem you're out of luck by official routes. The main website describes the ticketing structure and process, and the final dates have indeed passed.
A search on ebay reveals at least one seller of tickets, but I'd be very cautious buying tickets second-hand - not that it can't be done though.
Burning Man Festival itself organises a ticket exchange programme for those interested in reselling their tickets. They call it 'STEP' (Secure Ticket Exchange Program). However, for the 2012 festival this is now closed.
The Secure Ticket Exchange Program (STEP) is an online system that facilitates the safe resale of tickets that have been purchased directly from Burning Man. It's designed to provide a hassle-free, secure way of buying and selling tickets while avoiding scammers, counterfeits and scalpers.
Tickets for concerts and events are often resold on eBay but it's a bit of a dodgy avenue. I would suggest looking at a dedicated ticket resale site like StubHub's page for Burning Man Festival. Resale avenues are pretty much a sellers' market so these tickets could be significantly more expensive; however, keep an eye out because sometimes new tickets get listed for resale from people who may be willing to settle for less.
At worst, you could always go to Burning Man and then buy a ticket from a scalper. There's a reason why they are named that - so how much you end up paying them depends on how good you're at bargaining! (Hint: dress down, don't "look rich".)
It should go without saying that buying in the open market is a bad idea, but don't forget Craigslist.