Here is the current release of my small 3d engine.

From the README.txt :
The aim of this project is to provide a set of functions for writing 3d games. By 3d i mean "true" 3d (not raycasting as used in some FPS).

The main features of this engine are :

• Polygon-based (triangles) rendering.
• Affine Texture-mapping.
• Backface culling and Z-buffer sorting.
• Skeletal animation support.
• Import tools for Half-Life SMD file format (vertices and animation frames) which means that you can use well-known tools for 3d modelling, such as MilkShape 3D (http://www.swissquake.ch/chumbalum-soft/), 3DS Max (http://www.discreet.com/) with Valve plugin, etc.
• Uses GBA graphic Mode 3, 4 and 5 (thanks to subbie for this last one).
• Makefiles for both Linux and Windows.
• Pogoshell plugin (thanks to Sean Reid (http://seanreid.ca/)).

Download it here