I'm late to the party, but Joe Gregorio is writing a column on building RESTful applications for O'Reilly. I particularly liked the article describing how to build a RESTful bookmark service, sort of like plumbing for a del.icio.us knockoff. I wonder how much better, worse, and/or different del.icio.us would be with similar design.
Hat tip to Ryan Tomayko's link blog.