The users have to face a challenge and a correct answer would result in a new handset as the prize. The contest is up and running, which closes on December 16.
This Samsung Nexus S is the best creation of Google which has Android 2.3 Gingerbread and has amazing features like a 4 inch touch screen of 480 x 800, 1GHz hummingbird processor, Wi-Fi/3G networks, GPS and a 5 mega pixel camera on the back with a VGA camera on the front for video conferencing.
To win Google Nexus S for free all you have do is just follow googlenexus on twitter.
To know more about the contest rules check this LINK.