Over the last couple of weeks, I have found myself working with LaTeX an immense amount. From composing lab reports to writing handbooks, I have become rather familiar with the type-setting language in a rather short amount of time. It offers a wide variety of features to those who are willing to join its' rather cult-like community.
It is rather simple to get started and is an excellent, highly extensible tool which offers a substantial degree of control over the composition of documentation. Your most basic structural component is a section in LaTeX.