Debian Wheezy for sight-impaired.
"The installation process has been greatly improved: Debian can now be installed using software speech, above all by visually impaired people who do not use a Braille device. Thanks to the combined efforts of a huge number of translators, the installation system is available in 73 languages, and more than a dozen of them are available for speech synthesis too."
This for the latest version of Debian Wheezy.