Post it on InkTip (about the only thing they're good for). I posted a short there a few years back which is now killing it on the Festival circuit and will screening at Comic-Con next week. Am I making money off it? No. But it's generating buzz.
Also, make sure you keep the underlying story rights. I've developed mine into a Pilot so if some Producer/Studio loves the short, it's me they have to talk to and not the director (they're going to be the ones getting all the awards and heat).