For personal emulation or projects! 
I only know how to do it on Vista, and you'll need: 
1. Wii Remote 
2. Bluetooth capable computer 
3. Windows Vista (I'm sure there are ways to do it on 7/XP) 
4. GlovePie (for actually playing games)
 
Step 1 
Go to Control Panel then select Bluetooth Devices 
 
Step 2 
Turn On your Bluetooth and Select "Add Bluetooth Device" or similar 
 
Step 3 
While there, hold down 1+2 on the WIi Remote.  
If your system finds your device it should come up as Nintendo RVL-CNT-01
 
Step 4 
Select Nintendo RVL-CNT-01 and click Next 
Then select "Pair Without Using Code" 
 
Vista will being to install driver software and your controller will now be visible in Bluetooth Devices 
 
Step 5 
Start up GlovePie 
and paste this into the first text tab window: 
 
Key.Up = Wiimote.Right
Key.Down = Wiimote.Left
Key.Left = Wiimote.Up
Key.Right = Wiimote.Down
Key.A = Wiimote.Two
Key.B = Wiimote.One
Key.Enter = Wiimote.Plus
Key.S = Wiimote.Minus


Key.Up = Classic.Up
Key.Down = Classic.Down
Key.Left = Classic.Left
Key.Right = Classic.Right
Key.A = Classic.a
Key.B = Classic.b
Key.X = Classic.x
Key.Y = Classic.y
Key.R = Classic.R
Key.T = Classic.ZR
Key.O = Classic.ZL
Key.L = Classic.L
Key.Enter = Classic.Plus
Key.S = Classic.Minus   
  
These are the controls for the Wiimote and keyboard. Now you have to go into your emulators and change the button to fit each other, or customize the controls how you like them. These are settings for both a Horizontal Wii Remote and Classic Controller support. 
 
Step 6 
Your controller probably went idle, so just hold 1+2 again and press RUN in GlovePie to begin the script. You should visually see on the controller that the script is running.
 
Step 7 
Play some vidyer gamez!!