I recently discovered vocalid.org thanks to a TED video[1]. They work to provide people having speech impairments with unique synthetic voices thanks to voice donors. According to their process, a voice donor need to read 2-3 hours of text to allow them to build a custom synthetic voice.

I don't know if they have any plan to open their data but if someone could find a way to increase the amount of voice donors while improving an open dataset, it would be interesting. Just a thought, they are most certainly many more issues / options in this field.

[1]http://www.ted.com/talks/rupal_patel_synthetic_voices_as_uni...