Yeah, Luminous Landscape's a great site, isn't it? Just don't buy the argument about focal length having no effect on depth of field. I've seen it
comprehensively mythbusted by Ctein on the Online Photographer (but if you read that, your head might explode. It's pretty dang techy. I just looked at the pictures).
Another good general-knowledge website for turning on the lightbulbs is
the Cambridge in Colour tutorials.