tries to sue Samsung
out of existence for various patent infringement claims, Samsung is busy trying to steal some of its rival's competitors away. Not just Apple, but anyone who's willing to switch to a Galaxy device (Galaxy S II, S III or Note). Samsung wants your business so bad that it's willing to pay up to $300 for your existing phone, which could help eliminate or take away some of the sting associated with Early Termination Fees and/or upgrading to a new phone before you're eligible.
The only smartphone that's worth the full $300 is Apple's 64GB iPhone 4S for AT&T. If you own the CDMA version, it will net you $250. The way it works is you request an instant quote from Samsung's upgrade website, purchase a new Samsung phone, and then mail in your old device within 30 days. Samsung will cut you a check for the agreed upon amount, provided what you sent in matched your description.
Android devices aren't worth quite as much, but can still bring in a pretty penny. HTC's Rezound, for example, is worth $200 if it's fully functional, without water damage, and doesn't have a cracked or otherwise busted screen. So is Motorola's Droid Razr Maxx. Nokia's Lumia 900 (Windows Phone) is also worth a pair of Benjamins, while HTC's One X will net your $175.