The "official" layout editor
From CEGUI Wiki - Crazy Eddie's GUI System (Open Source)
Welcome to the entry page with information on the "official" layout editor! This editor is supported by the team (scriptkid mainly) in a way that we will try to keep it in sync with the CEGUI library itself, and to add much-requested features if within our powers.
The editor has recently been ported from MFC (Windows only) to wxWidgets (multi-platform). There is now a Linux version in the CVS, in addition to the Windows version.
The following links should get you up and running with the editor. Have fun :-)