DropBox, Box.com, DocumentsToGo (excel, word, pdf), free books, YouVersion bible, cam scanner. As you can see most of my usage is directed toward business.
As far as a case I have the Logitech Ultrathin keyboard case that connects to the magnetic side of the Ipad4 and folds over to protect the glass. The keyboard also has a magnetic slot that the ipad4 will fasten to while in the typing position. A great addition to my Ipad4 and one I must say gives off a 'wow' factor every time I use it in public.