I picked one of these up from GameStop for $20.
It's wireless and contains an 8 way joystick and 10 buttons, and supports both XBox and Playstation.
Pros:
* Inexpensive
* Wireless
* Dual analog "sticks" (they actually look like trackballs, but function as analog sticks)
* Comfortable to use; just the right size
Cons:
* The button quality sucks
* Marginal joystick quality
* Battery compartment is external and stuck on the back of the unit; works, but aesthetically unpleasant
Planned Mods:
* Definitely replace all of the buttons with Happs
* I might replace the joystick if I can find one that will fit, the case is really shallow
* Move the battery compartment internal, and wire up a port for external charging
* Add a lexan overlay with graphics
Cost to mod: Perhaps $30