I have this one from Bear Motion. I believe it's made in China and sold by various vendors. Very good protection and good looking leather in various colors. (See url at the end of this post.)
I purchased one at an introductory price of $3 and was unable to get my iPad 2 to fit. Gave it a bad review on Amazon and planned to return it. To the company's credit, I was contacted within hours with an offer to replace the cover. They sent me a new one. Same story. Couldn't get the iPad into the cover. To my surprise they insisted on sending me a third one. Success. For the record, others have mentioned that it's a tight fit but once it's on...it is ON!
It now sells for $20 and does an excellent job of protecting the iPad. I glued this piece of metal to the back (from a feeler gauge) and the SmartCover is held in place magnetically.
I mention this one mainly because I've literally NEVER had a vendor so committed to making me happy. I was willing to let $3 purchase go but Bear Motion was not. If you buy from them they'll make you happy.
I've also used the Speck back protector (clear polycarbonate). Main advantage is the small piece of metal on the case that holds the SmartCover in place when it's folded back. Otherwise, I wouldn't recommend it. Scratched very easily.
The other case I've used is from ENKI. (
www.enkigear.com). Made in Michigan if you care about "made in USA." Thicker than the Speck and it doesn't scratch easily. Took them awhile to get their ****** together when they introduced the case but sent me a reworked version free of charge. It's a very good case.
http://www.amazon.com/Motion-Genuine-Leather-Cover-compatible/dp/B005DBO228/ref=pd_cp_e_0
P.S. The ZUM and MacAlley cases appear to be very good and unlike the cases above, they eliminate the risk of dropping the iPad if you accidentally try to pick it up by the SmartCover. On the other hand, that eliminates one of the benefits of the SmartCover, imo: the easily detachable screen cover. If you're willing to give up that feature to avoid the risk, the ZUM looks like a winner.