Athanor is the home site of TPMath which provides much of the numerical functionality of PopTools
The Ecological Methodology program by Charles Krebs has many useful tools.
Program MARK by Gary White is great piece of software for estimation of demographic parameters in marked populations. See also the links to Gary's lecture notes.
The Population Ecology site by Alexei Sharov has a comprehensive set of lecture notes and many links to other sites.
Manchester Metropolitan University has an online course in multivariate techniques.
ULM (Unified Life Models) is provides similar functions to PopTools in a command line environment.
Ben Bolker used to have a great set of lecture notes on ecological models and data analysis.
The CRAN site provides access to R ("GNU S") a (free) language and environment for statistical computing and graphics.
Ordination Methods for Ecologists - lots of links.
NtRand implements the Mersenne twister algorithm for generation of random variables in Excel - including multivariate correlated sequences.
Erich Neuwirth maintains a site dedicated to the use of spreadsheets for mathematics, science and statistics education and has also written an Excel interface to R (see the CRAN site).