It's a 1000x1000 "pixel board". Every 10 minutes (was 5) you can place down a single pixel of any colour of your choosing. This board is shared with everyone else, and had at its peak that I've noticed over 90,000 users.
We were one of the first communities to make a piece orchestrated together, since then a lot of communities have made some pixel art pieces. It's actually pretty impressive. There's two competing Mona Lisa art pieces at the moment, too.http://reddit.com/r/place
"Jokes on them, I was only pretending to be retarded."
"With the first link, the chain is forged. The first speech censured... the first thought forbidden... the first freedom denied – chains us all irrevocably."