Do you know who Paul Falstad is?  If not, you really need to get to know him, or at least, his web site.  He’s a Geocacher, a Java programmer, and a Math nerd.  [Editor’s Note:  I don’t know Paul, I just read his web site.]  The easiest book mark I can access in my web browser is a link to one of Falstad’s applets:  A Circuit Simulation written in Java.  A very functional simulator, at that.