Links

Video

Graphing linear inequalities in two variables  (time: 3:24)
http://www.youtube.com/watch?v=VL7N2TOXVJk 

History

This is one of the best all around sites that I have found. It is titled "The MacTutor History of Mathematics Archive."
http://www-history.mcs.st-and.ac.uk/~history/

This is an award-winning site that links to all sorts of mathematics information.
http://archives.math.utk.edu/

Reference Topics

Here is a good site for graphing half-planes.
http://www.ltcconline.net/greenl/Courses/152a/functgraph/ineqgr.htm

This is an interactive site which will graph half-planes. Write the given inequality in the form

Ax + By < C
or Ax + By > C
with the inputs on the other row zeros.
If you want to graph an inequality with equality included, then draw the boundary solid rather than the shown dashed boundary.