Interceptor Entertainment (the developer behind the new Rise of the Triad game) and 3D Realms have teamed up to put the Duke Nukem platformers on Steam.
The Duke Nukem Platformer Pack costs $9.99, and contains three games. You can either buy the entire bundle or purchase each of the games separately at the following prices:
Duke Nukem 1 ($2.99)
Duke Nukem 2 ($2.99)
Duke Nukem: Manhattan Project ($5.99)