Thanks to a cool little promotion, the Populous-inspired Reprisal is free today in an effort to drum up support on Steam Greenlight. It's playable on Windows, Mac, and Linux, though the latter version is in beta. You don't have to vote for it to snag the freebie, but really, don't be that guy.
After a slew of higher-profile god games these past few years, Reprisal looks more directly reminiscent of the genre's earlier days; the days we still remember fondly. If all else fails, your ears will thank you for listening to the soundtrack.