This online text might serve as a good reference for basic concepts in statistics.

The authors of this book say that "The goal of this handbook is to help scientists and engineers incorporate statistical methods in their work as efficiently as possible."

arXiv is an e-print service, meaning that authors have submitted their research papers to this service. arXiv focuses on papers in physics, mathematics, non-linear science, computer science, quantitative biology, and statistics.

The Statistical Assessment Services is a nonprofit, non-partisan group whose aim is "to correct scientific misinformation in the media" and "to act as a resource for journalists and policy makers on major scientific issues and controversies."

This project, hosted by the University of Alabama Huntsville, says the goal of this site is "to provide free, high quality, interactive, web-based resources for students and teachers of probability and statistics."

A long-term project to make all systematic knowledge immediately computable by anyone. Enter your question or calculation and Wolfram Alpha uses its built-in algorithms and a growing collection of data to compute the answer.

STEW is an online resource for peer-reviewed lesson plans for K-12 teachers. The website is maintained by the ASA and accessible to K-12 teachers throughout the world.