This thread is for compiling a list of photoshop shortcuts
Here are some i've found and know of...
To apply the last-used filter:
CTRL + F
Apply the last-used filter with new settings:
CTRL + ALT + F
Close a working window Press:
CTRL + W
Copy a layer:
Hold ALT and click/drag on your canvas
To fill the area with the foreground colour:
ALT + BACKSPACE
Hide palettes and rulers:
TAB key to toggle the palettes between 'visible' and 'invisible'
Hide the marching ants:
CTRL+H
Hide the effects of a Mask layer:
Hold the SHIFT button and click the Mask layer icon
Invert a selection:
CTRL + SHIFT + I
Invert an image's colours:
Press CTRL + I
Quit:
CTRL + Q
Sharpen with Blur Tool:
ALT + Left Click and drag
Select All Text:
Press CTRL + A