Trading or selling keys:
Dungeons of Dredmor
SpaceChem
Frozen Synapse
HIB 3 (Crayon Physics Deluxe, Cogs, VVVVVV, Hammerfight, And Yet It Moves)
HIB 4 (Shank, Super Meat Boy, NightSky, Jamestown, Bit.Trip Runner)
HIB Introversion (Darwinia, DEFCON, Uplink, Multiwinia)