From the good folks at Internet Scout:
Does the mere mention of the phrase “sampling distributions” bring a tingle
to your spine? Visitors to this site will fear this basic concept of
statistics (along with many others) no longer, as it does a fine job of
explaining them in a fashion that is both lucid and jargon-free. Created and
maintained by Professor David M. Lane of Rice University, the HyperStat
Online site contains an online introductory statistics textbook, complete
with sections on normal distributions, confidence intervals, prediction, and
the logic of hypothesis testing. Each section contains a number of discrete
subsections, and users can feel free to browse around at their leisure.
Professor Lane has also included a number of external links to related
resources, including a visual statistics site by David Krus of Arizona State
University and a “Stat Primer”, authored by Bud Gerstman of San Jose State
University. Overall, this site is tremendously helpful, and will be of great
assistance to those entering the world of statistics for the first time.