Glen Moyes has made this fantastic video on Subdivision Surfaces (http://guerrillacg.org/home/3d-polygon-modeling/subdivision-surfaces-overview)
Subdivision Surfaces allow us to smooth a polygonal object to create nicely rounded models for both organic and mechanical models. This technique is widely used by artists because it allows us to use a low resolution model (called a hull or cage) which is converted to a high resolution rounded model. Subdivision surfaces also provide a the base for more complicated forms of modelling like Digital Sculpting.
And Paul McGrade has made a super video on Displacement and Bump mapping (http://guerrillacg.org/home/3d-texturing/displacement-and-bump-overview)...
In this video Paul McGrade explores bump and displacement maps. Both these types of maps affect the surface of our objects with a texture maps. Bump maps create the illusion of bumps, divets wrinkles etc without actually changing the actual geometry. Displacement maps change the actual geometry of an object but require more polygons and rendering time to achieve it's effect.
Coming Soon Videos
Euler Rotations Explained
3 Point Lighting
Basic Modelling Techniques