WooCommerce Sales Countdown is a fantastic plugin to promote your sale campaigns in WooCommerce. It shows a countdown box with the product on sale, to tell your customer how much time they have left to purchase your product with discount. You can also make it count the time till the up-coming sale period. WordPress 3.x and WooCommerce 2.x is required to install this lovely plugin for your shop.
Demo: http://codecanyon.net/item/woocommerce-sales-countdown/7906953