The good folks at GreenManGaming are putting up a 25% discount for all of their games in addition to whatever sales they have going on at the site.
Just type in the code 25OFF-ALLTH-EGAME whenever you checkout a game from GreenManGaming and you'll get a 25% discount.
The code has unlimited use and and it'll expire on July 9, so be sure to head on over to the site and buy some games while the offer's still available.
It should be noted that the code will even work on unreleased games like Hitman Absolution, Sleeping Dogs and Darksiders II, and newly released titles like Endless space. Most of the titles they carry are supported by Steam, so picking them up from GMG could be well worth your while.