Handling Shopp's shipping method selector in the cart. I couldn't find a decent action to hook into where 'is_cart_page()' also returned true, meaning that you can effectively have the shipping selector anywhere, although I have no idea what this will do - best just putting it in the cart ey ;)

Shopp Shipping.Methods in Cart

<?php
/
*
ADD THIS CODE TO YOUR FUNCTIONS.PHP
*/

add_action('shopp_init', 'shopp_cart_shipping_handling');
function shopp_cart_shipping_handling( )
{
	if ( array_key_exists('shipmethod', $_POST) )
	{        	
		$Shiprates = ShoppOrder()->Shiprates;
		$ShippingAddress = ShoppOrder()->Shipping;

		if ( !$Shiprates->disabled() )
		{
			if ( empty($ShippingAddress) )
				$ShippingAddress = new ShippingAddress();

			$selection = $_POST['shipmethod'];
			if ( $selection != $Shiprates->selected()->slug )
			{
				// Verify shipping method exists first
				if ( $Shiprates->exists($selection) )
				{
					$selected = $Shiprates->selected( $selection );

					$ShippingAddress->option = $selected->name;
					$ShippingAddress->method = $selected->slug;
				}
			}
		}
	}
}