Service Stack is a high-performance .NET web services framework (including a number of high-performance sub-components: see below) that simplifies the development of XML, JSON, JSV and WCF SOAP Web Services. For more info check out servicestack.net.
Developed in the modern age, Service Stack provides an alternate, cleaner POCO-driven way of creating web services.
Model-driven, code-first, friction-free development
No XML config, no code gen - convention-driven!
Smart. Infers intelligence from strongly typed DTOs
.Net and Mono
Highly testable - services are completely decoupled from HTTP
ServiceStack has been around for 4+ years
XML, JSON, SOAP and more!
Built-in validation - with smart fluent syntax!
Automatic Exception handling
Caching (**Memcached** and Redis are supported out-of-the box!)
Authentication/authorization (with built-in OAuth providers for Twitter/Facebook)
Read more: ServiceStack.net