I just gave a lightning talk at the fabulous code4lib conference. My boss at Atom Publishing Protocol was cool and how it could teach people about RESTful Web Services and HTTP (again). Here are the slides: http://kfahlgren.com/talks/code4lib2008/atompub_teaches_rest_http.pdf.
Apache Abdera is a great client and server in Java: http://incubator.apache.org/abdera/
I’m cleaning up the open-sourced O’Reilly Ruby client here: https://rubyforge.org/projects/atompubclient/
And the video is available here: http://www.archive.org/details/code4lib.conf.2008.lightningtalk.AtomPublishingProtocol