Tutorials in Soil Physics http://www.aquarien.com/sptutor/index.htm
These tutorials range in difficulty from college sophomore to the senior/graduate/postdoctoral level. They begin with the basics and extend to a new exact solution to Richards' equation for unsaturated horizontal and vertical flow.
Web Science http://webscience.nmsu.edu/
Interactive tutorials on soil taxonomy, texture and calculation of soil physical properties (New Mexico State University).