Representational state transfer (REST) is a style of software architecture for distributed hypermedia systems such as the World Wide Web. As such, it is not strictly a method for building what are sometimes called "web services." The terms “representational state transfer” and “REST” were introduced in 2000 in the doctoral dissertation of Roy Fielding, one of the principal authors of the Hypertext Transfer Protocol (HTTP) specification. For a quick introduction please start at: http://java.sun.com/developer/technicalArticles/WebServices/restful/  and/or http://en.wikipedia.org/wiki/Representational_State_Transfer and/or http://www.xml.com/lpt/a/2004/12/01/restful-web.html
Live services can be found at: http://restful.pats.no/terminal/

OMA / OneAPI reference implementations can be found at: http://group-lab.telenor.com/api/