If you don't use a Wacom tablet for your photography retouching - get one! I've had one for a couple of days and I can't see myself retouching without it again. Takes a bit to get used to, but as soon as you get the hang of it, it's great.
I bought one of the cheaper ones, the Wacom Intuos Pen Medium. Needed to save some cash for now. If you wanna take it up a notch, go for the Wacom Intuos Pro.
Keyboard shortcuts saves you time
Also, I set up my keyboard shortcuts based on how high-end retoucher Pratik Naik recommends it in his incredible class on Creative Live about high-end retouching.
I have slightly modified the setup for my own use:
Q - Increase brush size
W - Decrease brush size
A - Healing brush
S - Clone stamp
Z - Zoom
X - Switch foreground / background color
C - Brush
D - Rotate view
E - Eraser
This setup lets me use the left hand to control the tools and the right hand to use the pen. Saves a lot of time.
Adjust tablet settings
Also, disable the pressure sensitivity on the brushes, as it's too inaccurate (unless you have the dexterity of a surgeon). It's better to control brush size with the Q and W keys. You need to do this individually on each tool (go to the brushes panel).
To keep it short and sweet: Tablets help you work faster and more relaxed. This directly translate into more free time, more $$ or whatever you want it to do for you. I highly recommend using a tablet for any creative computer work!
You can get Wacom tablets on Amazon.