Today on Amazon, if you purchase $50 in select household goods, you'll get a $15 gift card for your trouble. The selection is limited to only a handful of items, but they're things like laundry detergent, batteries, and toilet paper that you need to buy anyway. [$15 Amazon Card with a $50 Household Purchase]
Update: The formatting on Amazon's page is really broken, so it might not be possible to see the gift card (or even all of the products) at all. Here's a link to the gift card to help you out, and you can make your browser window wider to see more of the product options.
Amazon's #1 selling external battery charger is only
$10 $12 today. It's definitely one of the smaller chargers around, but 3,000mAh should be good for a full smartphone charge on the go. [RAVPower Luster Lipstick Charger, $12]