Humble Weekly Sale is Codemasters crazy, offering four games (and one piece of DLC) from the studio's backlog for any price you want, plus three more games for $6 or more. The "pay anything" games are Overlord (and the Raising Hell DLC), Operation Flashpoint: Red River, Operation Flashpoint: Dragon Rising and Rise of the Argonauts. The $6 or more games are Dirt Showdown, Dirt 3 and Overlord 2. All games are PC and on Steam.
The charity that you can send all your money to this time around is Special Effect, a UK organization that helps people with all kinds of disabilities play video games.
Keep in mind that some of these games use Games for Windows Live, a service that is quickly becoming extinct. Dirt 3's GFWL systems are replaced with Steamworks, but Codemasters has no comment about its plans for both Operation Flashpoint games in this week's bundle.