freedomscientific.com, will let you download a trial version of JAWS, there assistive software for the blind.

it has a speach synthisizer built in, and will 'read'and articulte text... so you can have a professional reader read it!

the demo even lets you change the voice, from male to female, with several variations (Rocco, with an english accent is quite nice.) and yes, you can have US english (zee) or UK english (zed) (or sked ule vs shed ule for schedule)

the demo only works for a half hour at a time, it resets everytime you turn your computer on or off..
its is Windows driven, but they might have a Mac OS version too..