I thought RESTful services could not expose metadata (at least not in a way I could create a service reference against and generate a proxy). Either I am incorrect in thinking this, or Microsoft pulled off a miracle... A reference can be created to ListData.svc in IDE and a proxy generated. How can I pull off similar functionality offerings for my custom RESTful services?
The List Data service is an OData-compliant web service. The ODATA specification includes support for metadata. To build your own ODATA web service just use the .Net Framework 4 WCF Data Services. The framework generates metadata for your entity model automatically.
The List Data service is based on .Net 3.5 ADO.Net Data Services. To build a custom SharePoint OData service, you can use the SharePoint Data Services factory. I discuss the various data factories in my blog post at http://blog.sharepointbits.com/2010/04/custom-wcf-services-in-sharepoint-2010_17.html. The post doesn't include a sample of a Data Service but. I have a custom service sample I can provide if you want it.