To my students:  You may use the following utility to send me anonymous e-mail.  I offer it to you so that you may send me complaints, criticisms, or any other type of feedback that you might be reluctant to attach your name to.  On my honor, this utility is truly anonymous -- I am not tracking it in any way.  Please bear this in mind when sending me e-mail.  Since  I will not be able to respond to your message, please be as descriptive as possible.  If I receive an anonymous e-mail that says "the exam was unfair," I will not be able to get back to you for clarification, so tell me HOW you thought it was unfair. 

I hope this will help me to improve my courses, teaching style, etc., by giving me access to feedback that I would not otherwise have.   Thanks.