Are there any places that will let you host servers for free until you get a certain amount of usage?
Amazon EC2 offers you a great free server hosting solution. If you want integrated server hosting, Photon Cloud would work but be wary about what you use it for because it can’t run custom server logic. Forge has plans to provide customizable cloud server hosting in the future.
Yahoo Games Network (formerly Player.IO) is free until you reach a certain load level, then something like 10% of revenue after that. They allow hosting custom server logic, written in C#.