I stumbled across these things at Walmart a day or two ago, here's a video about them:
They're basically poseable lego-ish-size minifigures of an 'Aliens' warrior and a Colonial Marine, and they're pretty neat. They're made by Mega Blox/Mega Construx, the same company that does off-brand building block sets for Halo and Call of Duty. They both have articulation at the hips, knees, waist, shoulders, elbows, wrists, and head, and the Alien has an articulated tail. The Marine has a pulse rifle, combat knife, shoulder lamp, helmet, and his chest armor looks like it might be removeable as well. The Alien has these clip-on bits for the forearms to make it look like he's got giant "claws" (although I think they look a little goofy, and one of the fingers broke right when I was taking it out of the package), and a pair of facehuggers - one that has its legs all splayed out, and one molded to fit around the Marine's head if you remove his helmet.
They're $5 a pop and they're pretty neat, I certainly had no idea these things existed until I stumbled across them in the store. They're not even listed on the Mega Construx website as far as I can tell.
I'm hoping they sell well and we get more Aliens (and maybe even Predators).