Here are some lovely PSDs available for download; excellent for picking apart how to create great iPhone icons:
(Found via http://twitter.com/flyosity/status/15798736074.)
The gist of which is essentially you are creating a 57 x 57 icon and then adding one of the two following HTML lines to identify it:
The first option inherits the glossy light effect and corner radius from the iPhone OS. The 2nd one does not, so you have to handle corner radius and any desired light effects manually. iPad icons use 72 x 72 pixel resolution. I’m not sure yet, but I’m betting the new OS will have something closer to the 72 px size. Anyone know the answer?