We use ServiceStack with .NET and love it.

ServiceStack uses a HTTP cookie and supports a variety of authentication options out of the box, including basic auth.

https://github.com/ServiceStack/ServiceStack/wiki/Authentica...

We also use the easy hooks that ServiceStack offers to validate API developer / app tokens as well.

Social Bootstrap API is a backbone example:

https://github.com/ServiceStack/SocialBootstrapApi

https://github.com/ServiceStack/ServiceStack.Examples

http://stackoverflow.com/questions/15862634/in-what-order-ar...

It also has various other goodies, such as:

https://github.com/ServiceStack/ServiceStack/wiki/Metadata-p...

https://github.com/ServiceStack/ServiceStack/wiki/The-IoC-co...

https://github.com/ServiceStack/ServiceStack/wiki/Plugins

https://github.com/ServiceStack/ServiceStack/wiki/Clients-ov...

It also doesn't require ASP.NET and can run on Unix under Mono.

Try it, you won't go back to WebAPI is guarantee it!