Cheetah3D provides the most useful features you need to get the job done, and organises them within a beautifully elegant user interface that's powerful, intuitive and quick to work with. Performing truly advanced operations in Cheetah3D will seem like second nature very rapidly. Cheetah3D packs a terrific punch for it's tiny price. In fact, the program provides a level of productivity that you will be hard-pressed to equal in software ten times the cost!
Current Version: http://www.cheetah3d.com/download.php
Unity Documentation: http://unity3d.com/Documentation/Manual/HOWTO-ImportObjectCheetah3D.html
Unity Scale Calibration
1 unit in cheetah = 1 unit in Unity
Cheetah3d is a polygon/subdivision modelling app, with its own set of custom "modifiers"
Cheetah can create 2 UV sets per model, but can only display 1 at a time. It has full support for lightmapping, including radiosity, AO, and colour baking.
Cheetah supports Bones, Inverse kinematics.
Cheetah supports Unity friendly bone-based animation, and object based keyframing.
Exporting to Unity
If you save your Cheetah files into your asset folder and have your textures there too, Unity will automatically link the texture to the model. Apply Unity shaders to suit (Lightmapping etc).
It is recommended to save files as native .jas format, for convinience. Jas files can be used in unity, on a machine that does not have cheetah installed. For files which may be edited in another app, use .fbx (recommendation)