If you've ever used index cards to organize lots of notes or ideas, take a look at Index Card by Dennis Vogel. Available for iPad and iPhone, Index Card is ideal for researchers and fiction writers who need to put cards on a wall, but need that wall to go with them. A good example of skeumorphic design, Index Card is pretty much exactly like what you would use in real life, cork board background included.
In this episode of Origin Stories Dennis tells us how he came to create Index Card.