I've wanted a gamepad for my mac (mostly for playing emulators) but been too cheap or lazy to get one. Now that I have a PS3, I realized maybe I could just use that since it is USB/Bluetooth. I did a search here and couldn't find anything, so I thought I'd provide my experience getting it set up in case anyone else wanted to give it a shot.
First, you will need a driver. This guy wrote one a while back that seems to do the trick:
http://tattiebogle.net/index.php/Pro.../Ps3Controller It claims that Bluetooth support is coming but I believe its been a year or more with not one update. So it works, but only over USB.
Next, you need GamePad Companion to configure the buttons, etc:
http://www.carvware.com/ This is $15 shareware software, there might be alternatives that can do the same thing for less or even free.
Then after a reboot you can go into the GamePad prefpane and assign buttons on the controller to the keyboard. I was doing this first for an NES emulator so I just had to assign the D-pad, start/select, and X (for A) and O (for B). One annoyance here is that the buttons in the prefpane are labeled Button #1, #2, etc, so I will provide a map I wrote out to make it easier to assign them by identifying the actual PS3 button:
#1 = SELECT
#2 = L3
#3 = R3
#4 = START
#5 = DPAD UP
#6 = DPAD RIGHT
#7 = DPAD DOWN
#8 = DPAD LEFT
#9 = L2
#10 = R2
#11 = L1
#12 = R1
#13 = Triangle
#14 = Circle
#15 = X
#16 = Square
#17 = PS Button
#18-19 = nothing
Once you have that all plugged in, you probably want to save the config since different emulators will probably require different assignments. Now you click Start, and GamePad starts rerouting traffic for you. Load up your retro game and have some fun.
Top