I spread my grain into a 2x3x2 (l-w-h) open compost bin. I don't usually mix it in (i.e. with dried leaves), but I try to make as thin a layer as I can to increase the amount of oxygen and I've never have had a problem with it rotting and turning foul. It decomposes like a charm too.
As a side note, I was in Florida back in May and stopped by the Florida Brewing Company in Melbourne. They had giant 6 foot tall, 15-20 foot long dumpsters full of their spend grains, and let me tell you, it was possibly the most horrid odor I've ever had the displeasure to smell. They're lucky that the smell wasn't seeping into the tasting room. Compost properly and you can avoid your backyard smelling like death.