Belkin has announced a complete line of cases for the upcoming iPhone 3G. The Formed Leather Case offers slim, formed-leather construction, microfiber lining, and open access to the iPhone’s screen and controls. It will be available in black or pink for $30. An Eco-Conscious Formed Leather Case will also be offered, featuring a natural-felt interior and a price of $35. Belkin’s Leather Sleeve with Clip features form-fitting leather construction…