Magento Open Source, 1.9.x
Free Shipping Promotion

Free shipping can be offered as a promotion, either with, or without a coupon. A free shipping coupon, or voucher, can also be applied to customer pick-up orders, so the order can be invoiced and “shipped” to complete the workflow.

Some shipping carrier configurations give you the ability of offer free shipping based on a minimum order. To expand upon this basic capability, you can use shopping cart price rules to create complex conditions based on multiple product attributes, cart contents, and customer groups.