CF 3.5 introduces support for WCF.
Consuming using a WCF client
To create a CF WCF client you will need to generate it using the NetCFSvcUtil tool which is available as a part of the Power Toys download
Use this tool as you would for the desktop to generate a client.
Limitation: CF 3.5 only support basicHttpBinding. So in the Web.Config of your Service you will need to modify the binding attribute to binding="basicHttpBinding"
Limitation: CF 3.5 supports only Certificate credentials. You have no way of specifying / attaching username and password credentials on your request to the server.
Consuming using a Web Reference
the exposed WCF service can also be consumed as a standard web reference. Indeed for some time, this might also be the preferred way until WCF client matures.
To make your WCF service amenable for this sort of consumption, add the attribute
[ServiceContract(Namespace = "YourName"), XmlSerializerFormat]
Now simply add a web reference to the WCF service and you should be ready to go.
for more information check out these posts from Andrew Arnott