Steam News announces a free weekend is underway for Interstellar Marines, and when they say weekend in this case they mean week, as the first-person shooter is free from now until Sunday afternoon. The game is also on sale for 66% off during that period. Here's word on the game:

Interstellar Marines resurrects the old school tactical FPS, offering a unique blend of co-op, role-playing and non-linear gameplay. Set in a believable future, you take on the role of an elite soldier handpicked to join Project IM, a top secret military program being assembled to protect mankind from all dangers outside our solar system.