Tips on Photoshop/Camera etc

Just some nice link/collection:

44 essential digital camera tips and tricks
225 tips from famous photographers

99 Common Photography problems (and how to solved them):

1. General Photography Problems
2. Using lenses
3. Digital camera accessories
4. Digital camera settings and controls
5. Camera exposure
6. Using flash
7. Photography technique

If you want to improve your photo composition, read this article:
10 rules of photo composition

Photoshop:
20 things you need to know about Photoshop CS6: Click Here
6 photo editing steps every photographer should know