The new 1.1.3 firmware for the iPhone and iPodTouch brings with it the ability to add a ‘webclip’ from Safari to your home screen.
Thanks to this tip you can easily create a custom icon for people visiting your site, that works just like your favicon. Its just a shame you can’t add your own for other sites - I would love a custom Google Reader icon.
EXTRA : Having tried Nathans suggestion of 158x158px I can confirm that this size does indeed produce a crisper icon. Also, Drew has come come up with a way of using custom icons. I’ve put one up for Google Reader here