Meta-Wiki, located at meta.wikimedia.org, is billed as "the global community site for the Wikimedia projects and the Wikimedia movement in general". As you may recall, "Wikimedia" is the larger name given to the Wikipedia and its sister projects as a collective whole, administered by the Wikimedia Foundation.
As its name implies, this "Meta" wiki is an abstraction of Wikimedia initiatives and deals with the movement's mission, vision, and community. It hosts discussions and documentation about community activities, including analysis of on-wiki activities, offline coordinating, and future planning.
The main page displays announcements of upcoming events, including meetups by location, and numerous other links of interest to harcore Wikipedians. Want to see which Wikimedia projects have been closed? Here you go. You'll probably never need to visit Meta-Wiki—but now you know that you can.