Change filter name as its not neccessarily just for checkout.

readme.txt

@@ -166,7 +166,7 @@ Yes you can! Join in on our [GitHub repository](http://github.com/woothemes/wooc
 == Changelog ==
 
 = X =
-* Tweak - Made no shipping available messages filterable via woocommerce_cart_no_shipping_available_html and woocommerce_checkout_no_shipping_available_html
+* Tweak - Made no shipping available messages filterable via woocommerce_cart_no_shipping_available_html and woocommerce_no_shipping_available_html
 
 = 2.0.4 - 18/03/2013 =
 * Tweak - Like my account, added order_count attribute to view order shortcode.

templates/cart/shipping-methods.php

@@ -64,12 +64,14 @@
 } else {
 
 	if ( ! $woocommerce->customer->get_shipping_country() || ! $woocommerce->customer->get_shipping_state() || ! $woocommerce->customer->get_shipping_postcode() ) {
+
 		echo '<p>' . __( 'Please fill in your details to see available shipping methods.', 'woocommerce' ) . '</p>';
+
 	} else {
 
 		$customer_location = $woocommerce->countries->countries[ $woocommerce->customer->get_shipping_country() ];
 
-		echo apply_filters( 'woocommerce_checkout_no_shipping_available_html',
+		echo apply_filters( 'woocommerce_no_shipping_available_html',
 			'<p>' .
 			sprintf( __( 'Sorry, it seems that there are no available shipping methods for your location (%s).', 'woocommerce' ) . ' ' . __( 'If you require assistance or wish to make alternate arrangements please contact us.', 'woocommerce' ), $customer_location ) .
 			'</p>'