Old but good, this podcast  on se-radio.net with Stefan Tilkov talks around the ideas of RESTful applications - why building applications this way makes them part of the web, rather than just "on" the web, and why the REST style exploits the existing architecture of the web.

There's also a great introduction to REST ideas at http://www.infoq.com/articles/rest-introduction.

I like the way Stefan characterises RESTful applications as being a specialisation of the REST principles - meaning that an application can provide the basic operations (allowing data to be read, caching observed, mime types honoured etc) but still having a level of functionality that can only be used by a client which understands the api more fully (so, POST operations that will create new domain objects, that require specific inputs, for example).

And there's a nice write up of some of the frequently-heard objections to REST at http://www.infoq.com/articles/tilkov-rest-doubts, describing how you can achieve things like asynchronous operations. Many of these techniques are things that we're currently using on projects at Talis.