You can grab a free copy of Medal of Honor: Pacific Assault right now on Origin.
Now and then, EA will offer up a free game to Origin members through its "On the House" program. Although there doesn't seem to be any sort of schedule as to when these games pop up, or how long they're available, it's still a free game. The newest free offering may look a little familiar: Medal of Honor: Pacific Assault, which was an On the House offering last March.
All you need to do to claim your free copy is log into your Origin account, click "Free Games" and "On the House." Once that's done, just click "Get it Now," and the game will be added to your account. You can find the game page here
Once you have the game, you'll be able to keep it forever, even after the promotion ends. Of course, you'll have to have Origin installed to install and play the game, so take that for what it's worth.