PETER WATSON  Every now and then you run across a program which does one thing and does it very well. Franklin lets you visualise electric fields: not just for the one or two special cases that you find in every text-book, but for any arrangement of electric charges in 2 or 3 dimensions. If you teach electricity at any level, you need it: I've used the OS-9 version for several years for teaching a large class of freshman students. V 1.7 is better in all ways.

Why not a perfect 5? Electric field lines have a direction, which one indicates by an arrow: Franklin doesn't draw them!  
(Version 1.7)