There is a website I have been toying around with recently called Secret Builders. In Secret Builders students explore a virtual world full of historical figures. Students can meet these figures as well as explore their houses to gain a better understanding about each figure.
Teachers can set up student accounts for free – and watch as students complete achievements in the virtual world. Teachers can also create quests with rewards for students – serving as an impetus for students to learn about specific historical figures they may be talking about in class.
I am going to have to work with it some more to fully understand its classroom uses – but it already appears to have an educational value.