Over on the "Mindoo Blog", Karsten Lehmann has started an XPages series about stripping back some of the Notes-centric pieces of XPages and working with the underlying structure, java beans, and more.  While this is more than most Domino only developers may need to get into, the exposure to the underside of how XPages work, JSF, and so on is a great tool in understanding how XPages work behind the scenes, and can help you to design better XPages applications.

Hop over to the first article in his XPages series, and give them a read (5 articles in the series so far.) Its promising to be good stuff.

Happy Coding.