In Photoshop you can easily merge all visible layers and put them on a new layer on top of everything else. All you do is use the shortcut Shift + Alt + Command + E (PC: Shift + Alt + Control + E) and you get your new layer at the top without destroying everything below.
Rate images in Bridge a whole lot faster by using the rating shortcuts. Select the image you wish to rate and hold down the Command (PC: Control) key while pressing any number from 0-5. The zero rating is the shortcut to null out the ratings and the 1-5 is the corresponding number of stars.
Whether you have your documents open in tabs or not you can cycle through them by using the shortcut Control + Tab (on both Mac and PC).
To be able to undo any cloning in the simplest way, create a new layer before you want to start to clone. In the clone brush toolbar set the Sample drop-down from Current Layer to either Current & Below or All Layers! This will sample from all layers or the layer below but still allow you to clone on that new layer!.
Whenever you can use the scrubby sliders to change values in a box you can use these shortcuts to speed it up. Holding down the Shift key will make the scrubber go very fast through the range while holding down the Option (PC: Alt) key will allow you to fine-tune the settings, slowing down the scrubber to move in small increments.