I found the coolest little Pocket PC calculator today. It's called SpaceTime. I can't believe that I hadn't found this earlier, but it's a very advanced graphing calculator for the Pocket PC. They have a special running right now, so I picked it up today for 40% off. Check it out here:
SpaceTime 1.6, a revolutionary graphing calculator for the Pocket PC empowers your mobile device with 2D, 3D, and 4D graphing and nearly all the mathematical capabilities of a TI-83 Calculator.