Mathematical Software to prepare class note

[Mathematical Software to prepare class note]

Can anyone write me what software you use to prepare lecture note? I am not asking Matlab, mathematica etc. I am looking easy way to draw two or three dimensional graphs.
Thanks

[Nick Rawlings]

If you have a Mac then the Grapher utility is excellent, it does 2d, 3d, parametric, vector fields, can animate parametric curves to see what direction they are going, I have it open all the time when working through Professor Guichard's book.  It is much easier to use than use than tools where you have to type in plot parameters like wxMaxima and Sage.