Firefox speaks soon

FoxyVoice
FoxyVoice is a Firefox extension that provides text-to-speech functionality using Microsoft Win32 Speech API. With FoxyVoice
you can listen to the page being read; or browse on one page and listen
to another page being read for higher degree of sensory overload. The
soothing voices that comes with SAPI also makes FoxyVoice a competent virtual hypnotist.
More info at http://foxyvoice.kenche.info/

Accessibar
Accessibar is a toolbar extension for the Mozilla
browser which aims at providing various accessibility features for
users who could benefit from them. These features primarily focus on
the dynamic manipulation of the visual display of the web page in
addition to the integration of a text to speech reader which can read
out loud the browser’s user interface as well as web page content.
More info at http://accessibar.mozdev.org/