I ran across this link today...

http://www.pixelgenius.com/tipsandtechniques.html

Here you will find a wide range of Photoshop tutorials and information (.pdf format) written by some of the biggest heavyweights in the field, including:

Jeff Schewe
Bruce Fraser
Martin Evening

...and others.

If you haven't read it yet and despite being a little out of date, the "History of Photoshop" by Jeff Schewe is a facinating read.

Happy reading...

~Danny~