Here are some protractors you can download, print, and use. I suggest printing on transparency film. These protractors should not be used on-screen because computer displays generally distort image dimensions in such a way as to make the measurements imprecise.
This is a conventional protactor for measurement of angles in degrees:
This is a protractor for measurement of quadrance and spread, Rational Trigonometry concepts presented by Dr. Norman Wildberger in is book, Divine Proportions: Rational Trigonometry to Universal Geometry.
This is another protractor for measurement of spread. I suspect that the Decimal Spread Protractor is more useful, but this one is also fun to try.
Copyright 2005 Michael Ossmann, http://www.ossmann.com/mike/.