http://nces.ed.gov/nceskids/
This is a good webpage for creating all types of graphs(line, bar, pie, etc.). It seems easier to use than Microsoft Excel.

http://gcalc.net/
This site doesn't have lesson plans but it's graphing calculator that I've used in class.

http://www.mathgoodies.com/lessons/toc_vol5.html
This site has 8 lesson plans on integers. A weak area for freshmen math students.

Dave's Short Course in Trigonometry
This site covers many of the basic trigonometric identies we cover in our high school trigonometry class. It contains many drawings done with java applets that can be manipulated by the mouse to show how angles and sides of triangles change. It also has many practice questions to go with each topic.