Earlier today Microsoft released the Web Services for Remote Portlets (WSRP) toolkit on MSDN Code Gallery as a unsupported sample for SharePoint under the Ms-PL license. As defined by OASIS, WSRP:
WSRP defines a set of interfaces and related semantics which standardize interactions with components providing user-facing markup, including the processing of user interactions with that markup. This allows applications to consume such components as providing a portion of the overall user application without having to write unique code for interacting with each component.
SharePoint already included a WSRP consumer component. The toolkit includes the capability to implement the producer side. Included in the toolkit you'll find (1) a Visual Studio sample project that different approaches to create WSRP output from SharePoint, (2) a whitepaper documenting the architectural approaches and (3) screencasts.
Good to see this effort as there are those customers who have asked for this. However I'm happy to see Microsoft have more focus on technologies that do a better job in delivering on portal interop such as XML, RSS, REST and CMIS.