I've been using onepass shopping portal for bestbuy. 3mi per $. I pick up at the store if there is no free shipping.
It takes several weeks to post but if you return, it's bye bye points.
However, I have purchased AE and Macy's thorough both skymiles and aa's portals...returned the unwanted items to the local stores and the miles stay. Each time enjoyed free shipping.

Does anyone else have any luck with other stores for returning and keeping bonus miles?