Are you going to Startup Riot 2011?

There are definitely a bunch of options near the venue including the Westin which has a rotating restaurant (warning: expensive!) at the top so you can see the entire city in about an hour or a Holiday Inn just a block over. Keep in mind that the after-party runs to 7pm so depending on how much you drink, you'll want to choose your place to stay based on that.

Not sure if there are any places on airbnb.com that are useful. Since I live in Atlanta I haven't had to try. I have stayed at the Twelve Hotel at Atlantic Station (which is a bit far but there is a Twelve Hotel at Centennial Park which is much closer) and those rooms are really nice. You can get a 2-bedroom suite with a full kitchen and living room and then potentially have a lot more people in there especially since you'd have 2 full bathrooms.

Actually, there are some pretty nice places on airbnb.com. If you do that, you should go with one near a MARTA station since there is a MARTA station a block from the Tabernacle. That way you won't have to drive or find a parking spot at the venue. Which will be way more convenient.