IoC comparison: Autoregistration in Castle Windsor
Castle Windsor emphasises autoregistration, probably more than any other .Net IoC container, and the API to do it is probably the most complete.
Windsor's explicitness about registration - the lack of automatic resolution of unregistered concrete types - turns out to be an asset with autoregistration. In a sense, automatic registration and automatic resolution are two different approaches to the same problem of convention over configuration in that they allow you to create types without mentioning them in the container configuration. But they don't play that well together, and can give confusing results.