[Some of] Photoshop's keyboard shortcuts....

Photoshop is a program that everyone and their dog uses, so most of these shortcuts are well known to most people. Keyboard shortcuts uses up your free hand so that you don't have to waste time moving the mouse off the drawing area. BTW these are CS4 shortcuts so not all of them will work [but most will]

Single Letter Commands: By hitting one of these letters it will immediately take you the related tool. Handy if switching back and forth between drawing and erasing. Most tools have different modes, to specify which mode you want right click the tool on the toolbar and select the mode [in this menu it also shows you the letter command]. I've been nice enough to put an asterisk beside the most handy ones.

A- Path Selection/Direct Selection Tool

*B- Brush tools

C- Crop/Slice Tool

*E- Eraser Tools

F- Toggle Fullscreen Mode [to add to this, pressing Tab turns on/off the toolbars

*G- Gradient/Paint Bucket Tool

*H- Hand Tool [holding down the spacebar also activates this tool]

*I- Eyedropper [color selection] Tools [holding down the alt button by itself also activates this tool]

J- Healing Brush

K- 3D Tools

L- Lasso Tools

*M-Marque [selection] Tools

N- more 3D Tools

O- Dodge/Burn/Sponge Tool

P- Pen Tools

Q- Swap between RGB and Quick Mask

R- Rotate view Tool

S- Stamp Tools

*T- Text Tools

*U- Line/Shape Tools

*V- Move Tool [holding down the ctrl button by itself also activates this tool]

*W- Wand Tools

***X- Swap between primary and background color [highlighted cause I just discovered this today]

Y- History Tool

Z- Zoom Tool

Ctrl+ Shortcuts: These are a bit more generic but some are still unique to Photoshop. By pressing the Ctrl and the following letters will activate the following commands.

A- Select All

B- Color Balance

C- Copy

D- Deselect

F- activate the last Filter used

I- Invert colors

J- Duplicate Layer

K- Preferences Menu

L- Levels Adjustment Menu

M- Curves Adjustment Menu

N- New file

O- Open file

P- Print menu

Q- Close Photoshop

R- Show/Hide Rulers

S- Save

T-Free Transform

U- Hue/Saturation Adjustment Menu

V- Paste

W- Close current file

Y- Step Forward

Z- Undo

1- Zoom to 100%

2- RGB mode

3- Red only

4- Green only

5- Blue only

0- Zoom to fit screen

+- Zoom in

-- Zoom out

[note ctrl Z and ctrl Y work a bit different than you think in PS. Pressing ctrl Z will undo the last command and pressing it again will redo the command you just undid. By pressing ctrl+alt+Z you will undo continuously while ctrl Y will carry you in the opposite direction, hence why its called Step Forward]

Other: yea so if I went all of Photoshop's keyboard shortcuts this would go on forever. So these are some of the more commonly used [cheat code like] shortcuts.

Ctrl+Alt+I - Adjust Image Size

Ctrl+Alt+C - Adjust Canvas Size

Alt+Ctrl+Shift+B - Black and White

Shift + Ctrl + U - Desaturate

Ctrl+Shift+N - New Layer

F12 - Revert image to original state

F5 - Brushes menu

F6 - Colors menu

F7 - Layers menu

delete - Deletes active layer/selected area

i think thats it