The articles from the "RESTful Web" series at xml.com are a great
introduction.
The author (Joe Gregorio, of The Atom Publishing Protocol fame) also
regularly publishes insightful articles about all things REST on his
weblog. "RESTify DayTrader" (REST
Architecture applied to a benchmark stock trading application) is a good starting point. I also like "Why so many Python web frameworks?", which shows the implementation of a small restful web framework in Python.
