California State University
Cal State San Bernardino: Linear Regression
Cal State San Bernardino offers an excellent site on linear regression, including formulas and an applet that allows you to mark the locations of ordered pairs and then determines the equation of the regression line and graphs it.
National Council of Teachers of Mathematics
Nctm: Illuminations: Linear Regression 1
An interactive program where students will explore regression lines. Students will be introduced to the correlation coefficient and come to understand what it represents through the given exploration. Requires Java.