We've had a few iPad stands that we've talked about on TUAW, and all of them do the same thing to one extent or another -- they prop up the iPad so that you can view the screen without holding the device in your hand or lay it down on a desk.
EasyStand for iPad is a $19.99 device that is simple, well-made, and does exactly what it is supposed to do. The device comes in two colors, Metallic Black and Metallic Silver, and features two slots that are at slightly different angles. If the angle at which your iPad is being held seems too steep, just turn the EasyStand around and pop the iPad in the other slot. Both slots are felt-lined to protect your iPad, and there's a tiny "finger notch" that makes pressing the Home button possible without moving the iPad from the stand.
I was initially concerned that the hard material of the EasyStand would make it susceptible to sliding on hard surfaces like desks and countertops, but found that there are four non-skid bumper feet included that can be installed on the bottom of the stand. With the feet installed, the stand is not going to move. The bumper feet also keep the stand from scratching wood desks if you happen to get something sharp trapped underneath.