Using REST for Web Services, Instead of SOAP
Amit Asaravala wrote an interesting piece for DevX.com called Giving SOAP a REST. In it, he explains that REST means "Representational State Transfer" and that it is a serious alternative to SOAP ("Simple Object Access Protocol"). Both of these are protocols for web services.
What's the difference between REST and SOAP and why should you care?
REST is more an old philosophy than a new technology. Whereas SOAP looks to jump-start the next phase of Internet development with a host of new specifications, the REST philosophy espouses that the existing principles and protocols of the Web are enough to create robust Web services. This means that developers who understand HTTP and XML can start building Web services right away, without needing any toolkits beyond what they normally use for Internet application development.
The key to the REST methodology is to write Web services using an interface that is already well known and widely used: the URI....
This is a great article that helps to define REST for people who are seeing the term used for the first time. It also provides some high level discussion of the pros and cons of REST versus SOAP, and argues that REST is rapidly becoming a nearly complete alternative to SOAP as a web services protocol.