Mark Choate has released an early version of RDF Schema Editor for download. Giving it a quick run, it seems fairly intuitive for those who are used to RDF.
Schema Editor update "There is nothing like a real project when it comes to learning something new. The most problematic part of RDF from a user's perspective is handling namespaces. It's a hassle. But I also think that it's a hassle that can be overcome, and not one that really needs to intrude on the user experience. Improving the usability of tools that create metadata is important if the Semantic Web is ever to grow beyond speculation."