I'm currently building a Magento (1.9) webstore for a client who requires a flat rate shipping price to be applied to an order on a 'Per Unique Attribute Value' basis.
The functionality I need is to multiply the flat rate shipping price by the number of different values for the given attribute of the items in the shopping cart.
For example, on a flat rate shipping price of £3, if there were 4 unique values for the 'manufacturer' attribute in the cart, the shipping price would be calculated as £12.
Note that this is not the 'Per Item' type, but I do see the shipping calculation being somewhat similar. Ultimately I'm a relative newbie to Magento and so do not know exactly how to add the functionality I need.