Ubisoft games on GOG are half price.

All games are DRM free, lots of extras (no they don't redeem on steam).

Speed Busters: American Highways $2.99

Before the intrawebs was invented for people to shoot each other in the face online, games used to have this thing called a 'story'.
Some great classics and indie titles on offer.

From 1999, the PC Classic Sid Meiers Alpha Centauri for $2.39

strategy / turn-based / sci-fi

*Includes the Sid Meier's Alien Crossfire expansion.

Some great deals here for some classic games. All $2.39 unless marked below.

ULTIMA UNDERWORLD 1+2
ULTIMA 1+2+3
ULTIMA 4+5+6
ULTIMA 7 THE COMPLETE EDITION
ULTIMA 8 GOLD EDITION

Many great games, DRM-free and pre-configured to work on modern most operating systems, so just buy, install and play.

SAM & MAX BEYOND TIME AND SPACE $4.49
SAM & MAX SAVE THE WORLD $4.49
SAM & MAX: THE DEVIL’S PLAYHOUSE $5.24
BACK TO THE FUTURE: THE GAME $3.74
WALLACE & GROMIT'S GRAND ADVENTURES $2.99

Lots of good games, DRM free:

FALLOUT $4.99
FALLOUT 2 $4.99
FALLOUT TACTICS $4.99
FREESPACE + EXPANSION $2.99
FREESPACE 2 $4.99
DESCENT + DESCENT 2 $4.99
DESCENT 3 + EXPANSION $4.99

Gog have the updated version of Raptor: Call of the Shadows on sale. DRM Free and all of that, great game.

The discount increases with the number of purchases (including prior purchases).

Many great games:

BALDUR'S GATE 2 COMPLETE
BALDUR'S GATE: THE ORIGINAL SAGA
ICEWIND DALE 2 COMPLETE

MASTER OF ORION 1+2 $2.39
MASTER OF ORION 3 $3.99
ROLLERCOASTER TYCOON 2: TRIPLE THRILL PACK $3.99
ROLLERCOASTER TYCOON 3: PLATINUM! $7.99
ROLLERCOASTER TYCOON: DELUXE $1.59

A trip down memory lane here…

TERMINAL VELOCITY
$2.39

DUKE NUKEM 1+2
$2.39

DUKE NUKEM 3D: ATOMIC EDITION
$2.39

DUKE NUKEM: MANHATTAN PROJECT
$2.39

BLAKE STONE: PLANET STRIKE

This is one amazing game - I loved playing it as a kid - and this version includes all of the expansion packs.
You can download it for $3.99 from gog.com

I think some of these have been cheaper on Steam (Tomb Raider games) but there's a good range here and all games are DRM-free.

HITMAN: CODENAME 47 $4.99
HITMAN 2: SILENT ASSASSIN $4.99