ASP.NET is not available on Free Hosting (nor is classic ASP, for anyone who reads this).
At the moment, ASP.NET is available on paid plans, but keep in mind that it is only available through
Mono -- the servers don't run Windows/IIS with the .NET framework -- and that means that you basically get Framework 2 and 3 without the Win-specific APIs, and only some parts of MVC and AJAX (and, as far as I know, no support for LINQ at all yet). So before you consider upgrading or purchasing a plan (anywhere) that offers ASP.NET, make sure first that Mono support will be adequate for your application. If you require full support for MVC or LINQ, you'll need to look at Windows-based hosting.