Xnormal is a free program that allows you to bake many kinds of maps into
your texture,mostly used for games related stuff
afaik.You can generate and
manipulate normal,cavity,ambient occlusion and other maps and it can help
to convert displacement maps done with ZBrushs proprietary mappings to
conventional UV mapping for instance.
Ambient Occlusion combined with a texture (baking) should give a model more
plasticity.Certain aspects of a structure,like corners and bottom roundings and
where a model touches the ground etc,get enhanced and thus help imitating
a natural lighting or better the perception thereof.Similar to some drawing or
painting techniques that emphasize the readability of shapes.
And since TGs AO solution has much room for improvement I suggested to use
an other app.
The above is,of course, just a personal opinion.
Keep it rolling,Jochen.