Steam is giving you a double dose of savings with Midweek Madness
this time. Controversial indie game
Dear Esther (or is it a walking tour, I'm not sure which?) is half off, going for $4.99. If you're in the mood for something a little more traditional, the tower defense classic
Plants vs. Zombies is 75% off, or a measly $2.49. Considering the amount of gameplay you can get out of Plants vs. Zombies, that's quite a steal.