I found these tips whilst looking for photoshop brushes to download and thought it might be useful.
15 Photoshop Tips that you may not have known
1. Increase the Canvas Size with Crop Tool:We usually use Crop Tool (C) the images, but holding down Ctrl + Alt whilst dragging the Crop Tool to quickly increase the canvas size of a image from all the 4 sides.
2. Duplicate a Layer Style:To quickly duplicate or to copy and paste a layer style to a object on another layer,just hold down Alt key and drag on the "fx" which indicates layer styles. Alternatively if you just want to move a layer style just drag the "fx" and drop the layer where you want it to move.
3. Toggle between several open documents:If you have more than one documents open at same time, you can quickly toggle through them pressing Ctrl + Tab keys.
4. Layer Visibility:To hide all the layers except just one, hold down Alt key and click on the Eye Icon on the Layer Palette, this will hide all the other layer. To again make all the layers visible just do the same.
5. Select Alternative Layers:
Now, I am sure you might know that selecting a layer and then clicking on some other layer whilst holding down Shift Key selects all the consecutive layers between them, BUT if you just want to select say Layer 1 and Layer 3 and maybe just Layer 6, then just hold down Ctrl key and click on the layer which you want to select in the Layer Palette, this way only the alternative layers (i.e only the layers that you want) will be selected.
6. See The Text Color:
When you’re working with type, the obvious way to change color is to highlight the text and then pick a new hue by double-clicking the Foreground Color and choosing from the Color Picker. But the problem with this method is, because the text is highlighted, you can’t see the color change. To get around this, click the color square in the Options Bar. As you change the color, you’ll see the type alter accordingly.
7. Plotting Points on Curves:Curves can play a great role on perfecting the tones in a image, and you can end up with a lot of different effects simply by playing about with the Curves dialog. You can plot the specific color(s), just open up dialog box and hold down Ctrl key and click on any color in your image, a point will appear on the curve that represents the color, ready for you to edit.
8. Reset Any Dialogue Box:You can easily Reset any open dialogue box, press Alt key and click on Cancel button which has automatically become a Reset button when you pressed the Alt key.
9. Centre Point of a Document:A quick trick for finding the centre of an object is to Go to Edit>Free Transform and you’ll see a bounding box appear. There’s a useful handle in the centre of the top, bottom and side lines, so go to View>Rulers and then pull out to those guides. Alternatively you can use the following Photoshop Action I have made especially to locate the guides to the centre point of the document.
10. Do away with Palettes, Toolbox and Option Bar:Hit the Tab key and all the Palettes, Toolbox and Option Bar will disappear. This is particularly useful when you just want the image to be on the artboard, hit Tab again to get them all back. Alternatively, if you just want to do away with only Palettes hold down Shift key and hit Tab.
11. Image on a Specific Angle:If you ever want to get an image to follow a specific angle, with your image open, go to the Measure Tool (I) and click and drag a line to the angle you want. Now go to the Edit menu select Transform>Rotate. The layer will then snap to the line you drew.
Note:Remember that your layer should not be locked.
12. Add, Rename or Delete a Swatch:Right click on a swatch in Swatch Palette to quickly create a new Swatch or rename it or delete it. Another tip to quickly delete a swatch.
Hold down Alt key and notice how the cursor changes into Scissor icon allowing you to delete a swatch.
Same is true for Brush, Style Palette etc.
13. Move and Transform Selection:Drag on the document with the Marquee Tool (M) without releasing the mouse, hold down Spacebar, it will let you move the selection anywhere you like.
Also, you can transform a Selection by choosing Select>Transform Selection.
14. Scale Layer Style/Effects:If you apply a layer style to a object and are picky like me to have it only this much or just that much, worry not, you can easily adjust how much of a layer style to be applied by Right clicking on Layer Style icons (fx) and choosing Scale Effect, in the corresponding dialogue box you can easily scale effects by moving the slider.
15. Open a Layered File as a Flattened Image:If you want to just have a quick look at the file, it can be a time consuming task waiting for all the layers to load, if your file has lots of layers. But there is a nifty trick to turn it around, Go to File>Open and find the layered file you want. Before clicking Open, hold down Shift+Alt and Photoshop will open a flattened version of that file.