Microsoft : SpeechAPI 4(0.9MB)

Text-to-Speech Engines :
Mary, Mike, Sam and More (7.3MB)
American English (0.99MB)
British English (2.54MB)
Dutch(2.58MB)
French(2.24MB)
German(2.18MB)
Italian(1.97MB)
Japanese(3.00MB)
Korean(3.03MB)
Portuguese (2.39MB)
Russian(2.85MB)
Spanish (2.36MB)
Elan Speech Engine
Eloquent Technology ETI-Eloquence
IBM ViaVoice Outloud
AT&T Natural Voices