So I'm bored again, waiting for some files to turn up. So I thought I would just post a bunch of Photoshop tips and shortcuts off the top of my head, as there are hundreds of ways to improve your productivity in PS of which these are a good selection. So in no particular order, here are a random bunch of these tips (WRITTEN FOR CS2, SOME MIGHT NOT WORK IN OTHER VERSIONS)

Holding down ALT while using the move key will create a copy of the layer which you then move.

Holding down ALT + SHIFT on a thumbnail while opening a .psd from within Photoshop will open a flattened version of the file, useful for big files when you only want the flat version.

Holding down ALT while cicking on a thumbnail of a layer mask will show you the mask in the main view window.

Holding down CTRL before using the move tool and then clicking on an object will automatically select the layer that that object is in. However Photoshop can get confused if a lot of blending modes/opacities are being used and it might not be able to work out the layer you actually want.

Holding down CTRL + SHIFT before using the move tool and clicking on multiple layers will select all of the layers that you click on.

Clicking inbetween letters while using the Type tool, then holding down ALT and using the left and right cursor keys allow you to adjust the kerning between letters precisely.

You can move layer masks from one layer to another just by clicking and dragging their thumbnails between layers. Holding down ALT while doing it will copy the mask rather than move it.

To complete a transformation, just double click inside the transform box area, or press enter if the box is too small. Pressing escape will get you out of transformation mode and revert you to the original version.

Holding down ALT and clicking on the eye next to a layers thumbnail will turn off the visibility of all other layers. Clicking it again returns it to the previous state.

Holding down SHIFT while using the move tool locks the movement to the x or y axis.

Holding down ALT while using the polygon lasso tool then clicking and moving the mouse switches to normal lasso until you release the mouse button.

Change layer opacity quickly by using the number keys. Pressing 5 will set it to 50%, 8 to 80% etc. Pressing 2 numbers quickly allows you to do inbetweens, eg pressing 4 and then 5 quickly sets it to 45%.

Double clicking within Photoshop, but outside of a canvas window opens the open dialogue.

Holding down ALT while using the brush tool temporarily selects the eye dropper tool.

Use multiple layer masks on one layer by putting it into an empty layer group and adding a mask to that. You can then stack up groups inside eachother and get even more.

Holding down ALT while adding a layer mask automatically makes it the opposite of whatever you have selected.

CTRL + SHIFT + F is the fade command, learn it, use it. One of the most important tools in PS.

phew enough for now I think, if you want to add your own I don't mind, but try and not make them completely obvious ones like ctrl + d being deselect or something, this ain't a noobie forum!