Now we're Talking! Read4Me reads documents using a variety of voices (in 27 languages with Lion). You can save the audio to file. Proof reading documents by listening will help you catch issues that a spell checker won't.
Read4Me opens Microsoft Word, Open Office, RTF, HTML and other text documents, and it is very easy to change the speed of reading in words per minute, or to start, stop and select another voice.
Voice Coach is a unique feature of Read4me that allows you to embed pauses, pitch & rate changes into your text. Voice Coach tagging is essential in creating AudioBooks for poetry. Tagging is not always fully supported by all voices, but the classic voices can even sing with this feature (almost), other effects work best on the novelty voices.
Installing additional voices can be a bit confusing. The Read4me support page on my website has a movie that shows exactly how to do this.