Oh, I got my hands on some great training series from Lynda.com called Photoshop CS4 for Photographers: Creative Color. It’s really awesome. Chris Orwig is going through some really useful techniques for color correction, and I’ve learned some great new shortcuts (Mac). I bet you didn’t know this:
Shift+Alt+Command+E = Copy a merged version of all underlying layers into one single new layer on top of those. This is quite useful when color correcting and you need a merged version to further experiment on, without having to permanently merge the work you’ve done up ’till that point.
Holding down Alt when adjusting the dark or light slighter of the Levels or Curves (and other?) will show you blown shadows or highlights. This is quite useful to avoid loosing color data in those areas of you image.
The following shortcut changes the blending mode of your currently selected layer, saving you the trouble of having to select it from the drop down menu in the layers palette. Here are some of the blending modes that I use the most (I think you need to select the Move Tool for theese shortcuts to work):
O = Overlay
M = Multiply
S = Screen
K = Darken
G = Lighten
B = Color Burn
Pressing D will change your colors to the defaults of Black / White.
Double clicking the “Background” layer while holding down the Alt key, will convert the background into a regular layer.