Radio Shack's Trade & Save program is nothing new, and we already know that the store will give you $100 toward the purchase of an HTC EVO 3D when you trade in an EVO 4G/Shift and $75 when you hand over an "eligible smartphone."
But what exactly is an eligible smartphone?
Well, apart from being a device that is fully functional with no broken components or water damage, it must be included in the list of 28 phones you see at right (click for larger view).
There are several different versions of iPhones, a hefty selection of HTC phones (ThunderBolt, Nexus One, and Droid Incredible 2 among them), the Motorola Atrix, a bunch of Samsung phones (including the Galaxy S 4G and Nexus S), and a trio of T-Mobile units (two made by HTC, one by Samsung). All of these devices will get you much more than $75 on eBay, Craigslist, Twitter, and forums, but if you'd rather just make the Shack your one-stop shop for ditching your old phone and picking up your new one, then there's the list for your reference.