Shaded Relief Maps
This is the grand-daddy site of them all. Put together and maintained by Tom Patterson of the US national park service, it's full of helpful advice and tutorials. Tom answers emails too!
Another useful site is here:
I just have to agree that shadedrelief.com is a wonderful site. We use the techniques presented there all the time at work, and Tom's "Natural Earth" imagery is one of the main inspirations for the design in my atlas. Plus he's an extremely helpful fellow.