Well there are loads but here are some which I like to use.
- Ctrl + zoom in
- Ctrl - Zoom out
- Ctrl Alt Z Move back one step
- Ctrl Shift Z Move forward one step
- Ctrl A Select the entire image
- Ctrl C Copy the selection
- Ctrl V Paste the selection
- Ctrl L Levels
- Ctrl M Curves
- Ctrl B Colour balance
- Ctrl U Hue/saturation
- From within levels or curves: - Ctrl 1 Red channel Ctrl 2 Green channel Ctrl 3 Blue channel
- Ctrl H Hides the selection marquee (the selection is still there and will reappear if you press Ctrl H again)