Found @ http://blogof.francescomugnai.com/2008/06/photoshop_secrets_revealed/
Every graphic designer works with secrets shortcuts or tricks that should never be told, like a magician 
But…as always, i have no secrets with you so here you have 20 tricks save-time.
Have fun and if you want…share in the comments other tips!
1) If you hold down ALT+CTRL+SHIFT (Mac: CMD+OPT+SHIFT) while starting Photoshop you can reset all the Photoshop settings back to factory default. Very usefull if you have problems with some tools or the interface.
2) One of my favorites. ALT+Click on the “eye” icon in the layer’s palette to hide all other layers.
3) Do you have trouble to find the cursor when you work with large canvases?
Simply press the spacebar and you’ll see the hand icon where the cursor is located.
4) When you are applying a “drop shadow” layer effect, try to leave open the dialog box.
You’ll be able to move the shadow with a simple drag and drop.
5) With a CTRL+Click on the triangle icon you can collapse or expand all layer groups
6) Another cool shortcut. Press CTRL+ALT+SHIFT+E
(Mac: CMD+OPT+SHIFT+E) to paste all the visible layers in a new one.
7) When you are in a dialog box, try to hold ALT(Mac: OPT) to transform the “cancel” button into a “reset” button. It doesnt work everywhere.
If you want to transform a path into a selection you have to press CTRL+ENTER (Mac: CMD-ENTER).
9) CTRL+ALT+Z (Mac: CTRL+OPT+ Z) to undo more than once.
10) Double Click on the stage (the gray area) to open a file or CTRL+Double Click to create a new file.
11) If you hold SHIFT while you click “File -> close”, Photoshop will close all the open windows at the same time.
12) ALT+CLICK (Mac: OPT+Click) a tool to switch through the related tools. For example, try ALT+Click (Mac: OPT+Click) on the Paint bucket tool, you will obtain the gradient tool.
13) CTRL+Click on the new layer incon to create a new layer immediately below the current layer.
14) Whit SHIFT+CTRL+ALT+T (Mac: SHIFT+CMD+OPT+T) you can repeat and clone the last transformation (made with CTRL+T).
15) To find the center of a document select the background layer and click CTRL+T (Mac: CMD+T) to see a crosshair in the middle. Now you can simply drag out a guide in this point to find the center.
16) When you have a selection hold CTRL and use the arrows to move it, one pixel at a time.
Use CTRL+SHIFT to move the selection by 10×10 pixels. With CTRL+SHIFT+D (Mac: CMD+SHIFT+T) you can load the last selection used.
17) Choose CTRL+0 to “zoom to fit”, CTRL+ALT+0 to “zoom to 100%”.
If you prefer you can zoom back to 100% pressing the space bar and then right click -> actual pixels.
18) With the type tool active press CTRL+T (mAC: CMD+T) to show and hide the respective palette.
Press CTRL+H (Mac: CMD+H) while a text is selected to show and hide the selection.
19) If you are working with the paint bucket tool, hold down ALT(OPT) to switch temporarily to the eyedropper tool.
20) To draw a straight line with the brush tool click where you want, hold down shift and then click again where you want.
Instead, to draw a dotted line you have to open the brush palette (hit F5) and from the “Brush Tip Shape” tab you have to set the “spacing” to 150%.
After that you can repeat the previous step like a normal straight line.
