Digital Tutors has two free Mudbox tutorials, one on Symmetry and one on Local Subdivision at their website.
For those who don't know what Mudbox is:
"Mudbox is the first advanced, high resolution brush-based 3D sculpting software that is built from the ground up to address the needs of the professional digital sculptor.
Designed by production artists for production artists, Mudbox introduces new ideas and combines familiar concepts in fresh ways to offer a unique solution for high-end commercial modeling and design.
With its friendly interface, consistent structure, respect for industry convention, and a "get it done" focus, Mudbox is quick to learn and easy to use, integrating seamlessly with existing pipelines. Digital artists with previous 3D experience are quickly productive in Mudbox with minimal or even no orientation."