I cannot recommend Zagg Full Body coverage highly enough. While it is a bit pricey, it keeps idevices looking great. While the ipad doesn't seem to be the scratch magnet that is the ipod touch, I still wouldn't want to risk my device.
That being said, I'm not putting it on the ipad 1 I purchased. It's a year old and the previous owner had it in the case over that year, and there are no scratches. (this would not be the case with ipod touch)
Without a real case, I would definitely recommend Zagg. Also, I hear their antiglare screen protectors are quite nice (I've only used the clear ones on my ipod, which are also nice).
Be sure to use a coupon when ordering from zagg. You can usually get anywhere between 20-50% off.