There are several tools, like TTSReader, which can be used to read text aloud.
Good in TTSReader:
- Can change voice
- including other languages
- Can change speed and pitch
- Can save speech as wav or mp3 file
Unfortunately it is difficult to find good and pleasant human like voices 😉
Better quality human voices are commercial products. AT&T provides a demo site for testing different voices.
For non-english languages, one could install eSpeak.
There are some online text-to-speech services. One multilanguage example is here. Just paste your text and listen yourself.
Update 2014: In MS Windows, there is now a Speech Platform, which supports 26 languages. The voice quality is good (as compared with eSpeak). For more information, see blog article.