Apple?s Speech Recognition and Speech Synthesis Technologies now give speech-savvy applications the power to carry out your voice commands, and even speak back to you in plain English, and now, Spanish. http://www.apple.com/macosx/features/speech/
Converts any written text into speech using Elan Sayso text-to-speech technology. Speechissimo can speak multiple common languages. For Mac OS X. http://www.speechissimo.com/