The WSRP Toolkit for Sharepoint contains two sample implementations of a WSRP producer for SharePoint. The first approach is based on a WSRP Producer that uses the HTML generated by SharePoint WebParts to render its content on a remote Portal using the WSRP standard.
The second approach is based on an ASP.NET page that, through a GridView control, can render the content of SharePoint Lists. A customized WSRP Producer is then used to expose the content to a remote Portal.
The Toolkit includes the source code for both solutions and a whitepaper on SharePoint interoperability using the WSRP Standard.