The Future of Web Services | ASP.NET 2.0 Illustrated

WSE 3.0, in many ways, is only a stepping stone to the future platform for service-oriented applications, which is Windows Communication Framework (WCF), code-named Indigo. WCF takes a similar view in that service-based communication should be easy, and is aimed at bringing us into the era of Service Oriented Programming. Service Oriented Programming (SOP) has four key tenets:

Boundaries are explicit. Developers will opt in to exposing, defining, and consuming public-facing services.
Services are autonomous. Services are consumers, and are independently versioned, deployed, operated, and secured.
Share schema and contract, not classes. Data never include behavior; objects with data and behavior are local to applications.
Compatibility based upon protocol. Capabilities and requirements are represented by a unique public name.

WCF is backward-compatible with existing Web Service technologies and can be implemented with a few simple attributes. In fact, it's possible to take an existing ASP.NET Web Service and expose it to both existing clients and WCF clients with only a few attributes and configuration. At the time of writing, WCF is available as a Technology Preview, but it does have a GO Live license, so you can use it in your code right now. You can find more information, and links to the download, at http://www.windowcommunication.net/.