In this video, Salman Khan of Khan Academy explains standard deviation.
Khan Academy

In this video, Salman Khan of Khan Academy explains sample variance.
Khan Academy

In this video, Salman Khan of Khan Academy explains variance of a population.
Khan Academy

Site has a program where you can input data values and it will calculate the mean, standard deviation, or plot data on a histogram.
WebMath

Gives a brief introduction and overview of the fundamental statistic concepts.
University of South Carolina

Descriptive Statistics topics
Wolfram MathWorld

In this video, Salman Khan of Khan Academy explains the normal distribution.
Khan Academy

In this video, Salman Khan of Khan Academy explains binomial distribution. Part 2 of 4.
Khan Academy

In this video, Salman Khan of Khan Academy explains binomial distribution. Part 1 of 4.
Khan Academy

In this video, Salman Khan of Khan Academy explains alternate variance formulas.
Khan Academy
