the Humble store has Red Orchestra: Ostfront 41-45 for PC and Linux, and Red Orchestra 2: Heroes of Stalingrad GOTY for PC, available for $1 or more. Pay more than the average (currently less than $3) and also grab Killing Floor and some of its DLC.
As with all Humble purchases, the money goes to charities Child's Play and the Electronic Frontier Foundation, the developers and the Humble store itself, in whichever breakdown you choose. Each game also comes with its original soundtrack, at no extra charge. Unless you decide you want one.
The Humble Mobile Bundle sale is also live now for one more week, featuring Android games Contre Jour, Anomaly Korea, Plants vs. Zombies, Bladeslinger, locked games Metal Slug 3 and The Room, and three new additions: Funky Smugglers, Raiden Legacy and Another World. Pay more than the average to get those last five goodies.