This was launch about a week ago but is going to be re-launched in the next few days as they didn't expect it to be so popular. Something like 5 million people world wide aer playing it.

Basically it is monopoly on google maps. You can buy nearly any street in the entire world and then build all kinds of houses on them. You also get chance cards to build special buildings or pay fines etc. I only just signed up to get the idea of it before it resets but certainly seems like a bit of fun. http://www.monopolycitystreets.com/