Defiance Games (you may have known some of the DG guys from the Wargames Factory debacle) has just released a free set of rules for their Alien Wars universe. It can be found here: http://www.defiancegames.com/index.php/alien-war
. I recently purchased a couple boxes of their USAC Marines and they are very nicely sculpted. Their Hudson's Bugs remind me of the Skitters off the TV show Falling Skies and feature some really nice chitinous aliens.