IBM’s alphaWorks: aDesigner: “The aDesigner is a disability simulator that helps Web designers ensure that their pages are accessible and usable by the visually impaired.
Voice browsers and screen readers read aloud the text on Web pages and are used by visually impaired people. However, these devices are less effective with certain kinds of content, such as highly graphical material. Web developers can use aDesigner to test the accessibility and usability of Web pages for low-vision and blind people.”
This is a free tool and works only on Windows XP and 2000.