In the new adapters series I discussed the adapters released with BizTalk Server 2013. I demonstrated the relay adapters (HTTP, NetTcp), Service Bus Messaging, WebHttp (REST) and linked to the TechNet Wiki article on SFTP. I have written a White paper that discusses the BasicHttpRelay more in-depth. You can find it here:
http://go.biztalk360.com/wcf-basichttprelay-adapter/
Cheers,
Steef-Jan