There does not seem to specifically be a Blu-ray 3D sale going on to link to, but as part of overall price drops for the season it seems like there's finally a decent selection available for under $20 and even under $15, so I think it's worth sharing. These prices are in flux, though; not all I link below are the same as when I first saw them, and they might not be the same by the time you try them.
$12.49 Conan the Barbarian http://www.amazon.com/Conan-Barbarian-Two-Disc-Combo-Blu-ray/dp/B004EPYZTE
$12.99 The Green Hornet http://www.amazon.com/Green-Hornet-Three-Disc-Combo-Blu-ray/dp/B002ZG99BI
$14.96 Abraham Lincoln: Vampire Hunter http://www.amazon.com/Abraham-Lincoln-Vampire-Hunter-Blu-ray/dp/B008NEMPTO
$14.96 The Adventures of Tintin http://www.amazon.com/Adventures-Tintin-Three-Disc-Combo-Blu-ray/dp/B00701897I