I love the camera on the iPhone 4, but I've always disliked digital zoom and do whatever I can to avoid using it. Photojojo has responded to my inner camera snob with two glass lenses that can be attached to the phone via a magnetic ring.
You can always rig an existing camera lens to your phone, and the progress on the iPhone DSLR project is amazing, but this looks to be a more portable solution. A fisheye lens is available for $25 and a wide angle/macro lens is $20. You can get both together for $40.
Be warned that the lens does cover
