The Marware Sidewinder Deluxe iPhone Case is certainly the most cord-friendly iPhone case ever. Instead of you winding the earphone cord around the phone itself or just cramming them in a ball, the Sidewinder give you a spot on the side of the case to hold the cord neatly. The cord holder actually retracts back into the protective case (as you can see on the left above) so you can slip your iPhone into your pocket easily. The scratch-resistant shell case also includes a belt clip, screen protector, and microfiber cleaning cloth. A pretty good deal for an iPhone case for a bit over $20.
thanks fenstar!