Cmd/Ctrl+Shift+Alt+E will merge a copy of all Layers
F Cycle through workspace backgrounds
X Change your foreground and background colours
D Reset foreground and background colours to black and white
] and [ Change your brush tip size
Cmd/Ctrl+J Duplicate a layer or selection
Space Bar Hold Space and drag to navigate around the image
TAB Hides or shows all panels and tools
Cmd/Ctrl+T Transform a layer
Cmd/Ctrl+E Merge selected layer down, or merges several highlighted layers
Cmd/Ctrl/Ctrl+Shift+Opt+S Save for web & devices
Cmd/Ctrl+L Bring up levels box
Cmd/Ctrl+T Open Free Transform tool
Cmd/Ctrl+M Open Curves
Cmd/Ctrl+B Edit Colour Balance
Cmd/Ctrl+Shift+Opt+C Scale your image to your preferred state
Cmd/Ctrl+Opt+G Create clipping mask
Cmd/Ctrl+0 Fit on screen
Cmd/Ctrl+Shift+>/< Increase/decrease size of selected text by 2pts
Cmd/Ctrl+Option+Shift->/< Increase/decrease size of selected text by 10pts
]/[ Increase/decrease brush size
Shift+F5 Fill the selection
}/{ Increase/decrease brush hardness
,/. previous/next brush
</> First/last brush
Cmd/Ctrl+] Bring layers forward
Cmd/Ctrl+[ Send layer back
Cmd/Ctrl+Shift+[ Send layer to bottom of stack
Cmd/Ctrl+Shift+] Bring layer to bottom of stack
Author: S.K.Satheeshkumar,Eraniel.