Text-to-Speech Roleplaying options

[Taejang]

The sound of an NPC's voice can be fantastic for roleplaying. Accents, pitch, tone, it all lends itself well to setting the scene, and memorable voices instantly affect the players even months after they last heard it. Unfortunately, I can't do all the voices I want to do (like Mass Effect reaper, Skyrim daedric lord, or even just a convincing hispanic, though I'm working on that last one).

What computer programs, websites, or Android apps do you folks know of that will let me do text-to-speech (TTS)? It has to have multiple voices, effects (bonus points if it lets you layer two or more effects!), and preferably allow reading English in foreign accents (like Chinese or Irish). I could do a voice changer instead of TTS, but that makes it harder to do ad hoc during a game.

(So far, the best I've found is this site. Neat feature: setting 'pitch' to lowest gives a pretty good goa'uld.)