The October 2011 CTP of WCF Data Services adds powerful, but incomplete support for Actions. The motivation behind Actions stems from wanting to advertise in an OData entry an invocable ‘Action’ that has a side-effect on the OData service.
Actions will provide a way to inject behaviors into an otherwise data-centric model without confusing the data aspects of the model, while still staying true to the resource oriented underpinnings of OData.
-- dpblogs, MSDN
The tutorial on this new feature, which is useful to you Windows Phone developers out there as well, will take you through, Using WCF Data Services to Invoke an Action, Setting up a WCF Data Service with Actions, and the features that are coming soon.