A couple months ago I saw these gizmos at an event I attended. A bunch of electric car owners came to a public hearing on electric car infrastructure that was organized by a California State Senator.
FWIW I wrote this article from the meeting:- http://www.torquenews.com/1075/gm-and-nissan-trade-punches-over-electric-car-fast-charging
In any case out in the parking lot one of the guys had a few useful gizmos he was showing to help with charging Leaf's at public charging stations.
This is the basic idea. The white box is a J1772-to-NEMA-14-50 adapter box. It inputs J1772, outputs NEMA 14-50. These are normally sold for DIY electric car conversions, but it will play a role here with a Nissan Leaf.
The thingy plugged into the 14-50 socket splits it out to three 240 volt L-6-20 sockets. Very straightforward.
This shows it with a Leaf 120v charger plugged in. Many Leaf owners are getting their portable chargers modified for 240 volt operation at http://evseupgrade.com ..
The Leaf portable charger is limited to under 3kw or I think the max rate it'll support is 12 or 16 amps. Most of the public charging stations support 30 amps. This means you could run two (or maybe more) of the portable Leaf chargers off one public charging station. The way it works is by use of the splitter, you plug the converter box into the J1772 hose, plug in the splitter, then plug in portable chargers to the splitter.