Is best for Operation based Services ,building Interoperable services to work with such as Java, channel and host plug-ability,flow transactions, Security (Message, Transport), Support multiple binding such as HTTP, TCP, MSMQ, PIPE.
WCF Data Services :
This is formerly known as ADO.NET Data Services this is good example for implantation of OData (Open Data protocol ). This kind of services mainly used to expose data model as RESTful services.
WCF WEBHTTP Services :
Is best when you are exposing operation-centric HTTP services to be deployed at web scale or are building a RESTful service and want full control over the URI/format/protocol.
This is new to .NET 4.0 Framework to build project on this you need to download Project templates from online
First of up VS.NET 2010 go to Tools->Extension Manager->Online Gallery –>WCF and download .
WCF RIA Services:
WCF RIA Services is mainly used for building RIA Application example Silverlight.
WCF Workflow Services:
Is best for long running, durable operations or where the specification and enforcement of operation sequencing is important.