If you press the following keys in order, a picture of the screen will be written out to the Photos application on the Pre. The command is:
Orange key + Shift key + P key
To execute the command press and hold Orange, Shift, and then P. When you do, a new category will be shown in Photos called "screencaptures". From there, you can do whatever you want with the photo. The above photo was taken on my Pre as a test.