Radio Shack is out with a nice new coupon over on their Facebook Page. Just click on the wall post pertaining to this offer and they will email you a $10 coupon that can be used on any $20 purchase.
As you can see this is been quite a popular offer so far, as over 20,000 have already been requested! This coupon is valid through March 30th, so there is some time to use it. Like most deals such as this, make sure to read the fine print as there are a few exclusions that will apply.