Voices can be categorized as robotic and human voices. There are several robotic voices available for free download on this page. Robotic voices generate speech exclusivly by synthesis. Human voices are voices that are not entirely synthesized. They may be considered to have higher quality by certain users, depending on the intended use.
Robotic voices - free
* Included in the TTSReader installer. You shouldn't download this if you already downloaded the installable version of TTSReader.
Human voices - commercial
There are several companies offering human english voices. SpheNet is in no way associated with these companies, and cannot attest the quality of their products.