EDIT!
Backstory; Swapped my 60GB HDD for Xbox 360 for Need for Speed: Shift and a wired Xbox 360 Controller since I got a 120GB for free. Worked great, then I got curious.
I downloaded this program called XPadder. Neat little program. Map keys of a controller to any key you want. In my case, I mapped my Xbox 360 controller buttons for a couple different games.
Games: Diablo 2 and Zdaemon. Diablo 2 is perfected to my liking, and Zdaemon is still a work in progress. I started out by writing down all the 360 controller buttons, and chose which suited which. Obviously, it required a bit of work since I had to choose a key, load the game, and see how it worked out.
What I wrote down: (changes made, clear by the scribbles I made)

Now after I had most of it done, I finalized a XPadder config. I got it down to this:

Now, I can play Diablo 2 using my Xbox 360 controller. It isn't too bad just need to get used to it. I have all my buttons set as follows:
Left Stick::: Mouse Arrow
Right Stick::: Arrow Keys
A::: Left Mouse Click
X::: "T" Keystroke
B::: "C" Keystroke
Right Trigger::: Right Mouse Click
Left Trigger::: Right Alt Keystroke
Right Bumper::: "Q" Keystroke
Left Bumper::: "P" Keystroke
Start::: Tab Keystroke
Back::: Escape Keystroke
D-Pad Up::: "1" Keystroke
D-Pad Down::: "3" Keystroke
D-Pad Left::: "4" Keystroke
D-Pad Right::: "2" Keystroke
As for Zdaemon I'll get that up once it is finished. Here is a video I did showing me using the Xbox 360 Controller. Half showing the controller is in fact being used, and the other half of gameplay.
http://www.youtube.com/watch?v=aBy58-6wjEUAll in all, it took me about 2 hours to perfect a config for it. It may get tweaked later but for now it works great. Was fun to do. I may do other games as well for it.
-Tye