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. Now fixed in the current version.

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.