I have been using the same simple iphone case since the day I got my iphone4. Its a very think plastic 1 sided case; its gets the job done. Then on laughing squid I came across this Bookbook, an iphone case that doubles as a wallet and looks like a book. Pretty nice. The bookbook iphone case goes for $60.00 with free shipping. I have not actually seen this thing, so no idea how this will work day to day, but looks pretty cool.
The video they made to promote this thing pretty good, high production value. A bit cheesy at the end though.