eSpeak is a compact open source software speech synthesizer for English and other languages, for Linux and Windows.Discontinued
The last version (1.48) is from March 2014.
Gespeaker is a GTK+ frontend for espeak. It allows to play a text in many languages with settings for voice, pitch, volume, speed and word gap. The text played can also be recorded to WAV file.
Online Text to Speech by ReadSpeaker. Speech-enable web sites, mobile apps, online documents and forms so that your visitors can listen to your content.
Voice Dream Reader lets you listen to any document and ebook using text-to-speech.
A backend for gSpeech, also usable in media players. The technology has been purchased by a German company for use in BMW automobiles for text to speech, as well. It is also used for GooglePlay. The open source libraries are still available, however.
Fala - A simple text reader is an open source application. A simple software that speaks a text. You can type the text or appoint a file. Fala is just a frontend to festival. Its designed for GNOME, but if you have gtk, pyhton and festival you are able to run it.
Experience our world-class, natural-sounding, text-to-speech (TTS) software programs today. Empower your applications with advanced TTS software using VoiceTextTM. Robotic voices are now history!
The aim of the MBROLA project, initiated by the TCTS Lab of the Faculté Polytechnique de Mons (Belgium), is to obtain a set of speech synthesizers for as many languages as possible, and provide them free for non-commercial applications.
KMouth is a program which enables persons that cannot speak to let their computer speak, e.g. mute people or people who have lost their voice. It has a text input field and speaks the sentences that you enter. It also has support for user defined phrasebooks.