My buddy and University of Oklahoma colleague, Dr. Michael L. Kent, has a new book up on Kindle. Michael is a rhetorician and consult, in addition to being a professor in Public Relations.
The book is easy to read and has a history of public speaking as well as several chapters on what to consider and what to do if you're going to be speaking pubicly.
From the book description: Bare Bones Public Speaking offers a comprehensive, but stripped down version of a basic public speaking textbook. The book features substantive discussions of persuasive, informative, and special occasion speaking, as well as comprehensive treatments of ethics, visual aids, delivery, organization, logical fallacies, audience analysis, and other areas. Bare Bones Public Speaking also includes a comprehensive introduction that lays out the historical roots of public speaking and sets up the practice as a response to rhetorical situations and important social exigencies. At only 43,000 words, Bare Bones Public Speaking is about half as long as a standard public speaking textbook, but will still meet one-hundred percent of your needs. With clearly defined lists, sample outlines, links to prominent and timely speeches, and suggestions on how to succeed in a variety of communicative situations, Bare Bones Public Speaking offers features found only in the most expensive academic textbooks costing $75-100. Bare Bones Public Speaking is a new breed of textbook, suitable for an academic classroom environment, a communication professional interested in broadening his/her skill set, or a non-professional who just wants to learn how to be a more compelling and polished speaker.