ReadPlease is a fully-featured, easy-to-use, and natural sounding text-to-speech program that can read anything on your screen (as long as it can be copied onto the clipboard).
The basic voices that come with both versions are Microsoft Mike, Mary, and Sam, but there are hundreds of free international/multilingual Microsoft voices available for download. Each version supports customizable fonts and background colors as well as a low vision colour mode.
You can use ReadPlease to read your e-mail, documents, or favourite web pages. ReadPlease makes it easy to follow along since it highlights each word as it reads it.