Just saw this review of MagicPrefs on Macworld!
Adds boatloads of touch functionality to the Magic Mouse through a System Preferences pane. From the website:
Looks pretty good and best of all, it's free! Get it here!It features the ability to bind a variable number of finger clicks, taps, swipes, pinch and other gestures to functions like Middle Click , Hold Down Both Mouse Buttons , Spaces , Expose, Dashboard etc.
Tom (... I got mine!)