Is there a good program I can access online where I can plot points on a graph and get the equation of a line?

Question

I am a teacher and would like something that I can use as a class project where students can enter values for x and y and get an equation from a line. I would especially like it if it would make a trend line from a scatter plot. However just a simple online site that would allow them to type in x and y coordinates and get an equation would be good!

Answer 1

http://gotoscience.com/Calculator.html

http://www.coolmath.com/graphit/index.html