I came across a couple of interesting links today. The first one is a simple wizard-like tutorial for creating logos of letters.
The second one, Unleash.com , is a bigger resouce dedicated to all sorts of graphical issues – from logos to 3D. Practical examples mostly cover CorelDraw, but some of them are easy enough to reproduce in Photoshop. There is also plenty of practical theory, which can suggest ways of improving your photographic skills.