Have you had a look at http://calagator.org/ http://calagator.org/ It's mostly focused on Portland tech events at this time, and I don't know how well it would

Have you had a look at http://calagator.org/ http://calagator.org/ It's mostly focused on Portland tech events at this time, and I don't know how well it would scale up, it's also not a business, it's provided as a service to the community which means it's not operating under the same constraints you would face as a startup.