I am starting a direct sales business. I want to send a letter to everyone I know introducing what I am selling. How do I do that?

It sounds like you are wanting to put out a letter of introduction. The following sites are excellent for providing information to write letters of introduction.

Idea Cafe Small Business Archive: "Company introduction letter"

Introduction letter - Wikipedia, the free encyclopedia

cover letters - sales introduction letters and inventions ideas submissions

Introduction Letter... The key business letter for getting your foot in the door

Welcome to ASP web site - introduction letter