I got an ipad2 for Christmas so I had to do research into cases recently. I was reading on the macrumors forums and found a ton about cases there. There are a lot of different case styles available and they all have different features. I wanted versatility and protection so I chose a case from Maroo.
Here is a quick overview of what I found about cases:
Apple sells their smartcover that snaps on with magnets and covers the screen. It folds up into a triangle to hold the ipad at 2 different positions for typing or viewing. It does not protect the back. There are a lot of manufacturers that make very thin shells that snap onto the back of the ipad to protect the back from scratching but they don't provide much impact protection. A couple of these will actually lock the smartcover onto the ipad so if you are holding the cover and let go of the ipad it won't separate from the cover and fall.
There are a number of manufacturers that make an integrated product with folding front cover and thin shell back, to replace the smart cover and snap-on back mentioned above. You can find these on ebay and on amazon. They offer the same functionality and limited protection mentioned above.
There are a number of products that have thicker fronts and/or backs for more protection. The covers will fold once and connect to the back with tabs, slots, etc. to provide the dual positions for viewing or typing. I have seen some with the shell backs and some with thicker backs. The Maroo that I have is of this type, with padded front and back.
There are some cases that are book-type cases and provide good protection and look good for an executive business environment but don't provide the positions.
Most inexpensive cases are made from synthetic materials or some kind of split leather that looks more fake than real. Cases like this are available for $20-40. If you want something made from real leather that looks good for business use then it will cost closer to $100.
http://forums.macrumors.com/forumdisplay.php?f=139