USB Fever has released two new products for the iPhone. 
The Tri-image mirage/Sparkle/Starburst Lens (http://www.usbfever.com/index_eproduct_view.php?products_id=1849) is a $2.99 lens for the iPhone and iPhone 3GS. It comes with a back cover. You can detach the lens from the back cover if it’s not needed.

The Red/Green/Yellow Color Filter Lens for iPhone 3G/3Gs (http://www.usbfever.com/index_eproduct_view.php?products_id=1850) is a $23.99 lens and lens filter. It also comes with a back cover.