I have not run too many Structural Equation Modeling (SEM), so I can’t comment too much about this resource, but anytime I see something like SEM features added to R, I have to rejoice. This page gives a nice tutorial introduction to lavaan, the R package for SEM, and the material is pitched at a level easy to follow even for people like me who have a limited appreciation for SEM terminology.
Yves Rousseel. lavaan tutorial. Available in html format.
You can find an earlier version of this page on my blog.