In the spirit of Smithsonian Museums, who offer free admission everyday, Museum Day Live! is an annual event hosted by Smithsonian magazine in which participating museums across the country open their doors to anyone presenting a Museum Day Live! ticket… for free.
For 2014, Saturday September 27th is the day that has been selected. (If the museum is closed on Saturday their next business day they are eligible.)
The public can visit smithsonian.com/museumdaylive  to learn more, and download a Museum Day Live! ticket. Each ticket grants the ticketholder (plus a guest) free access to any participating museum on September 27. One ticket is permitted per household, per email address.
A list of participating museums can be found here .
For those of you who are local here are the museums included:
Virginia Sports Hall of Fame & Museum
Children’s Museum of Virginia
Hampton Roads Naval Museum (Free everyday)
Portsmouth Naval Shipyard Museum
Lightship Portsmouth Museum
Chrysler Museum of Art (Free everyday)
I am not sure that they run out of tickets but they have the right to stop issuing them at any time. If you commit now I would go ahead and reserve your pass!