I have used a program called Advanced Grapher to prepare graphs for papers, presentations, and one book. It costs $30 (I have enjoyed lifetime upgrades) and is currently available here
Plot graphs, perform regression analysis with Advanced Grapher
Fooplot ( www.fooplot.com ) will let you save graphs, and if you choose one of the vector formats (PDF, EPS, SVG) they will be fantastic for printing, though you need a program that supports vector image embedding. If you're doing your worksheets in LaTeX this is ideal. Fooplot also has PNG export for those using less-professional programs.
Desmos ( www.desmos.com ) seems to only let you save after logging in, though you could always screenshot it.
graph.tk ( graph.tk ) also lets you save, but doesn't support vector formats.