To use the Shopping Cart Promotion Rules to allow for Free Shipping follow the these steps:
1. Enable Free Shipping
Go to you System > Configuration > SALES > Shipping Methods > Free Shipping > Yes
Once Free Shipping is enabled add in the "Minimum Order Amount" = 100000000.99 ( This is important so it does not show for all orders but just for the promotional rules you apply Free Shipping on. If you do not add this "Minimum Order Amount" Free Shipping will display for all orders. )
2. Create Your Shopping Cart Price Rule
-Go to Promotions > Shopping Cart Price Rule > Add New Rule
-Apply the General rule info and if you want to have a coupon / time period for the promotion
3. Configure your Actions
We have put the discount amount to $0 but you can adjust this as needed.
The import part here is to offer " Free Shipping" = For shipment with matching items.
If you need any restrictions you can apply them below in the conditions to limit certain categories, price ranges, skus, brands, etc.