We just posted a great new tutorial titled “Building Project Facets” by Konstantin Komissarchik of BEA Systems on Eclipse Corner. If you want to know what facets are, and how you can use them to extend the capabilities of the Web Tools Platform, this tutorial will set you straight.
I’ve also recently published an article, “Eclipse RCP: A Platform for Building Platforms” on ONJava. I excerpted bits of this article for my position paper for the Rich Client Applications Symposium at Eclipse Summit Europe.