Plogue's Alter/Ego is a new voice synthesis platform. It's free and can run as standalone software, VST, AU, or RTAS/AAX plugin in 32 or 64 bits.
bedroomproducersblog.com
Type in what you want it to say/sing, and then every time it gets a midi note, it says the next syllable at that pitch. Does a pretty good job of parsing English text, but you can also type things in (pseudo)phonetically. My kid was using it to create songs in Elvish.