Site gives detailed information for constructing a least squares regression line.
Stat Trek.com

This site is designed to provide information, demonstrations, links and quizzes associated with the statistics and statistical methods for research design and analysis. It includes tuorials and applets
WebStat

Very comprehensive list of statistics formulas.
Stat Trek

The website indexes lectures in Introduction to Statistical Methods course.
Lecture Summaries: Introduction to Statistical Methods

It also gives formulas, description, etc for statistics.
Wolfram Mathworld

Interactive applet that allows a student to plot points on a graph and see how an outlier affects the regression line of the data points.
Illuminations NCTM

Site has defintion and explanation of the least squares regression line as well as links to additional resources.
Carlton College Statistics

Regression topics
Wolfram MathWorld
