Tree diversity analysis - A free manual and software for common statistical methods for ecological and biodiversity studies.
Resources for Python
Official page of NumPy The fundamental package needed for scientific computing with Python.
SciPy Another Python library that uses NumPy to do advanced math, signal processing, optimization, statistics. The list of staticical functions is provided here.
matplotlib A python 2D plotting library which produces publication quality figures.
R/SPlus - Python Interface An interface that allows Python code to call R functions and R code to create Python objects and call Python functions and methods.