IBM Home Page Reader is a talking browser designed for people with vision impairments.
Download the free 30-day trial (http://www-03.ibm.com/able/solution_offerings/hprtrial3.html) to hear your site spoken. This will enable you to fix the content of your web site so that it sounds correct to someone using a talking browser or screen reader.
HPR offers another testing advantage because it presents a web page in two different views. It places the graphics view, a true rendering of the web page, in the upper portion of the program window. Then, it shows a text view of the web page in a window below that graphics view. By looking at the text view, you'll gain an appreciation for what a blind user would hear when listening to your web page. HPR allows you to save the text view to a file.
The bad news is that HPR is no longer supported by or offered by IBM. But you can still download the trial (URL above). And it seems that some copies are still available on the Internet; for example Buy.com says they have HPR at $86.99, with this warning: "Very few left In Stock! Order soon -- product may sell out."
Both major screen reader companies, Freedom Scientific (JAWS) and GW-Micro (Window-Eyes) offer demo versions of their screen reading software. You can download and install the product and use it for about 30 minutes, but then it stops working; however, when you reboot your machine, you can use the screen reader again for approximately 30 minutes.