The Smart Back Cover
This case from iLuv fits squarely on the iPad 2, though it's definitely nowhere near as thin at its contenders. In fact, it actually kind of sticks out a bit on each corner.

The back has special coating that prevents it from getting scratched by everyday use, though there isn't a magnet to keep the flap back there if you want to e-read. In the grand scope of things, the iLuv Smart Back Cover is fine, but for $5 less you can get any other back cover that's thinner and serves the same purpose. ($39.99 | 3/5)

iFrogz iPad 2 Back Bone
We appreciate that iFrogz went against the norm when naming their "smart" back cover. The mold of this one resembles the one from iLuv, though it seems much more polished. It's obviously thinner than the iLuv and doesn't stick out as much on the corners, and there's even a plastic grill on the back speaker that prevents it from getting scratched.

Unfortunately, there's no magnet on this one either, so the flap will hang down if you're trying to read. And when you fold it over into the viewing stand, the iPad kind of stands straight up rather than at an angle, which would make me a little nervous if I were on a plane, or a very rocky boat, and I wanted to watch a flick on my iPad 2. ($34.99 | 3.5/5)

Incipio Smart Feather
Just like the regular Feather for iPad 2, the Incipio Smart Feather fits impeccably, almost as if it's a part of the tablet's original chassis. The Smart Feather is thin and doesn't protrude, and it actually snaps on over the Smart Cover so that it doesn't pop off.

When the Smart Cover is folded up into a stand, the matte finish on the back of the Smart Feather works in conjunction with it so that your iPad won't slip away. Though the Smart Feather is very thin, the bonding of the magnet to the Smart Cover isn't strong enough to keep the flap folded back. However, everything else about the Smart Feather checks out, and it's easily our favorite one for pairing with your Smart Cover. ($34.99 | 4.5/5)

Speck SmartShell
Speck's SmartShell has a smooth, matte finished that bonds well with the Smart Cover. It doesn't clip over the hinge, though, so the cover can still be easily pulled off, but the back has a magnetic strip so that the flap stays put and you can read through your Kindle book without too much hassle. The back portion also covers the bottom part of the iPad 2 -- a little more than the Incipio Smart Feather.

While the case is not as thin as other back covers, we like this as the second best. Just be sure to buy it in the color that matches your Smart Cover. ($34.95 | 4/5)