This weekend at Grand Old Games - GOG.com - you can buy Blake Stone: Aliens of Gold , Blake Stone: Planet Strike, Duke Nukem 3D: Atomic Edition , Duke Nukem: Manhattan Project and Rise of the Triad: Dark War for £1.85. All are DRM free and run through DosBox straight after installing. Duke Nukem 3D in particular is a classic and should tide you over till Forever comes out.
Come get some! Duke Nukem 3D Atomic and other Apogee games 50% off - £1.85 at GOG.com