Form of multi-family housing focused on community, sustainability, and growing and aging well. Most are owner-built and include common spaces intended to be used on a day-to-day basis.
There are 115 cohousing communities in 23 states in the US and many in other countries - the concept was brought to the US in the late 80s from Denmark. I live at Songaia Cohousing, a cohouding communiting of 35 people living on 11 acres in 15 homes near Seattle. Lots of info is available on the web.