Absolute best way to clean the iPad screen is dry, with the 3M Scotch Brite High Performance Cleaning Cloth. The cloth costs $3-4, but it is a woven microfiber that pulls fingerprints and dust off like nothing else. I've tried a number of different cloths, including those that came with my HD TV, etc. The 3M flat makes 'em feel like using a paper towel (NOT recommended...). And when it gets dirty? Toss it in the washing machine.
I actually went and bought a couple spares - one for the house, one for my briefcase, and one for the office - just so I'd always have the right cloth handy. The iPad is a great device; I'd prefer it not be a great fingerprint display as well.