Boxer briefs. A little on the tight side. And make sure you pull them up in the creases (think "frontal wedge-V").
My best luck so far has been with Starter Dri-Star poly boxer briefs from Walmart. They wick well, keep things dry, prevent the chaffing, last as well as any others I've had, and they're cheap (about $10). The down side is that they do hold the stink. I pack two pair (one on, one in the pack). I try to launder the pair I wore every night (in a zip-lock), but it's nice to have the second pair in case I can't get to the laundry. I go commando overnight (after washing up), so things can air out.
With this regimen, I've not needed any lubes, rubs, oils, pastes, or powders.