Back in the good old days of Atari's and Commodore64's there was a program called S.A.M. the software automated mouth. Considering this was available about 30 years ago I have always been dissapointed at the lack of progress in robotic speach since then.
I know there is some much better speech programs available now but how often have you had a computer talk to you?
S.A.M. is actually built into Adobe Reader. Just open a PDF file, go to the "View" menu and at the bottom you will find "Read Aloud".