Vocallective's NATA female voicebank for the Plogue Alter/Ego realtime voice synthesizer is now a free download
Site: https://nata.vocallective.net
Plogue Alter/Ego https://www.plogue.com/downloads.html#alterego
Announcement: https://www.twitter.com/vocallective
I haven't tried this yet so can't testify to how good/bad/easy/hard it is.