Rain Design makes one called the mStand. It's great. Well, almost great...it'd be "great" if they'd carve a notch in the front so you could operate the lid latch without lifting the MacBook up off the stand.

Actually, closing the lid until it's just open 1/2" or so is enough to put the MacBook to sleep, so it's not a big a deal (and you don't have to worry about the keys messing up the screen).

Since I wasn't using the laptop's build-in keyboard I kept putting papers on it, trying to use it as a copy stand. But the papers just slid right off. A specially trimmed plastic card (e.g., old hotel card-key) fixes that.