Some are rather basic, depends on if you are wanting to conjugate match the input and outputs of amplifiers. There are more out there as well, but this should get you started. I would also draw your attention to Qucs, http://qucs.sourceforge.net/ a freeware simulator, cheers, Richard
The one I've been using is really intuitive and gives a really clear result. Plus its web based so you can use it on your desktop or mobile (cell)www.will-kelsey.com/smith_chart
