At least in part by the efforts of Donna Ballman at the Screw You Guys I'm Going Home blog:

"The Obama Administration just announced that it will allow people on COBRA to enroll in ACA through July 1, 2014. You'll have to call 800-318-2596 and let them know you qualify for the special enrollment period. They'll activate the special enrollment for you and you can choose from the exchanges." (link)

Read the full explanation here.