Activision has launched their publishers sale on Steam over this weekend. The sale runs from April 15 to Monday, April 19 and has titles marked down as much as 75%.
Activision has published quite a few games, so that means a lot is marked down. Some of my favorites are the Geometry Wars games. The first title, Retro Evolved, is only $1.99, and the third title, Dimensions Evolved, is only $7.49.