There is a nice discount on GamersGate at the moment - check it right here!
Try to use this 20% off coupon on any of those games: GFDMAY20 Fallout 3: GOTY £4.99 (Edit: non-Steam) Baldur's Gate: Enhanced Edition £7.49 Risen 2: Dark Waters £4.99 The Lord of the Rings: War in the North £3.75 Magicka Collection Edition £5.99 Borderlands GOTY £4.99
Bran new Call of Juarez game: Gunslinger is available for pre-order on Green Man Gaming. The games goes for $11.25 for Europeans (at least I see the price in dollars) when you use this voucher: GMG25-5GT67-87HJ9. Non-Europeans can always use this 20% off voucher instead: GMG20-GGN5D-FC3NA. Call of Juarez: Bound in Blood comes with this for free but it's not Steam redeemable! - info thanks to @tyrisflare