Professional writers often read their work out loud to make sure it flows well and sounds coherent. If you want to kick back and have the reading done for you, then give Speak Clipboard a try.
This lightweight, free, open-source app is designed for Windows XP, but you should have no trouble with Vista (and presumably Windows 7) too, just install the .NET 1.1 framework. To make Speak Clipboard talk to you, simply copy text into your clipboard via Right-click -> Copy or Ctrl+C, then fire up the app. You can pause and resume Speak Clipboard or change the reading direction from right to left, all with a single click.
This cool tool appeals to more than just writers. It's a great app to help people with a visual impairment, and a neat way for kids to practice their reading and writing skills.
Click this link to download Speak Clipboard from http://www.speaktools.com.