ShiVa is an easy to learn commercial 3D game engine. There is a free version of the software that allows you to freely evaluate it. Android exports made from the free version will bare a watermark but there aren't any time limits etc.
The known list of Cortex games made using this engine:
When your game is finished, ShiVa gives you a barebones android project that can be opened in eclipse. The ODK can be implemented in seconds using the free Cortex Build System (courtesy of Hypercane Studios). The documentation for the build tool and a working sample project illustrating in-app purchasing and controller support are maintained in this open source repo.