A couple of IBMers who help develop the database/persistence components in WebSphere products have their own blog.
The WebSphere and Java Persistence blog discusses WAS and persistence (see WebSphere EJB 3.0 Feature Pack is GA). So far they're focusing on WAS's use of OpenJPA.
These guys also contribute to the WebSphere Community Blog, which isn't so specifically focused on persistence but on WebSphere products in general.
WebSphere and Java Persistence Blog