Even if Manic Digger looks dead, a new version has been released. No information about this new version has been released.
Manic Digger is a free sandbox game in which you build using square blocks made of varying elements and materials. You can build anything you can imagine using the default blocks Manic Digger offers.
You can download the latest version here: http://www.indiedb.com/games/manic-digger/downloads