First good deal:
http://www.gog.com/en/page/duke_promo/
Game:
Duke Nukem 3D + Manhattan Project
Price:
$8.98
Expires:
Monday, June 1
Great deal - if you download eDuke32, you'll be able to play Duke Nukem 3D with high detail textures and full mouse view + at any resolution you want. It's still a great fun game. Manhattan Project is a good bonus - it's a classic platform game with modern graphics. You can't go wrong.