Text to Speech Service is very good in the cases when you have too much text to read. Text to Speech Service can read most documents and convert text to MP3, WAV or in many other Audio Formats.
I have gathered a list of 6 Free Text to speech services. You should try them if you are searching for Free Text to speech service.

1) iSpeech.org:
iSpeech has revolutionized text to speech with our free service. Now anyone can listen to any text content with minimal effort, no software installation and no technical expertise.

2) yakitome.com:
Turn any text into mp3 for free using the world’s best text to speech technology. Multi-Lingual: English, Spanish, French, German. Listen to PDF, MS Word, html, RSS feeds, blogs, email and plain text.

3) naturalreaders.com:
Text to speech software for natural voice. Let your computer read most documents with Natural Voices and convert text to MP3, or text to WAV files, text to audio files, read text aloud, download free text to speech software now text readers, computer reader, Reader, online reader, talking text, voice text.

4) FreeTTS:
FreeTTS is a speech synthesis system written entirely in the JavaTM programming language. It is based upon Flite .FreeTTS includes:Core speech synthesis engine, Support for a number of voices, Support for importing voices from FestVox (US English only) and much more.

5) text-speech.com:
Alive Text to Speech is a Text-to-Speech software, which can read Text in any application, and convert text to speech, or convert text to MP3, WAV, OGG or VOX files. This text to speech lets you listen to the Text in Emails, web pages, news articles, PDF, Word or Excel Documents,etc.

6) ReadPlease:
ReadPlease – Software that allows your computer to talk – with AT&T Natural Voices – Let the web talk to you with this easy and free software that reads emails to you, puts text-to-speech and it’s, using real human voices.