"knowtes" fingering charts from simplyviolin.com. I don't generally like fingerboard charts because they require 'map-reading' skills and I prefer to spend my time teaching string playing skills. But if the student already thinks in this way, they can find it useful to map out the fingerboard. If I had to have one, I like how this one attempts to show a little of an angled perspective instead of looking straight down at the fingerboard.
This FREE cheat sheet is great to print out and hand to beginning string students: violin, viola, cello, and bass. I asked my students to keep this in their music folder so that they can reference it during rehearsal and when they're practicing at home.