Good communication is an essential part of being a manager. This includes oral skills, written skills, and the often-overlooked need to be an effective listener.
Books: Communicating at Work * Author: Adler, Ronald B.
Books: Business English: The Writing Skills You Need for Today's Workplace
*Author: Geffner, Andrea B.
Essentials of Business Communication *Author: Guffey, Mary Ellen
Get to the Point *Author: Danziger, Elizabeth
Online: The Art of the Executive Summary *
*These resources are free of charge.