I’ve really been digging into Plone Archetypes.
Here’s a list of archetype examples from the Archetype wiki. Sidni de Silva’s article about Archetypes for ZopeMag. Archetype’s Developer Guide (very long). Sidnei de Silva’s Quick Reference (which actually is not that quick!) Andy McKay writes about why Archetypes should be in XML format. Also, here’s a list of Archetype API’s and Mgarnsey on how to create your own custom content type.
A great visual diagram about all the components in plone and their file/slot/portlet references.