Autarchy of the Private Cave

MathIsFun offers nicely illustrated pages on math, algebra, geometry and maybe more.

For example, there is a step-by-step instruction on calculating variance and standard deviation for a set of measured dog heights, with a final picture (below) illustrating one-sigma distance from the mean. Unfortunately, concepts of normal distribution and %% of data points within each sigma range are not discussed, but that might as well be too much for a nice explanation. There are also animations, like this mean machine. Overall, MathIsFun is a nice resource for younglings.

If you ever need to glimpse at the properties of the Poisson distribution with lambda=0.16, or find the factorial of 6163338 (as a gamma function), then Wolfram|Alpha is a perfect tool for you (unless you have some math package at hand).

The motto of Wolfram|Alpha is Making the world’s knowledge computable. Basically, it is like Mathematica plus a growing corpus of factual numeric data, plus a system to interpret user’s input. This is a nice online reference and computation platform.