Lynn Shelton’s Humpday has been getting rave reviews ever since it premiered at Sundance earlier this year, where it was acquired by Magnolia Films. The movie basically takes the idea of a “bromance” to the most ridiculous level possible when two best friends decide to make an amateur porn together. It starts as a joke, but then becomes a challenge of sorts and a weird macho quest to prove that they’re not gay by doing just about the gayest thing possible: having sex together on camera.

The movie stars Mark Duplass, known for his involvement in the so-called “mumblecore” movement (he directed Baghead and starred in both The Puffy Chair and Hannah Takes the Stairs), and Joshua Leonard, who many will remember as Josh from The Blair Witch Project. A lot of the movie is improvised (which explains why there is no writing credit listed on IMDb) and apparently they didn’t even know ahead of time how it was going to end. Clearly this is not a film that everyone will get, but after watching the new trailer, I think it looks pretty funny and I am definitely intrigued. What do you think, will Humpday be the sleeper hit of 2009? The movie hits select theatres on July 10th; you can also watch the trailer in HD over at Apple.com.