Beta 1 of Ember 0.5.0 is now available, both in source form and as a package for Linux systems. A Windows version will be available later on.
Get the files from here:
If you compile from source you will also need the media, which can be obtained from here.
This version is the first to use CEGUI 0.5 and Ogre 1.4. It also includes a new entity editing framework which allows for real time authoring of the world.