A while back we built a Speakjet project for the Arduino. It allowed us to send sound effects, and program robotic speech to the speakers.
It wasn't terribly intuitive, programming it phonetically, so we added a text to speech ship, the TTS256. The Sparkfun shield we used wasn't designed for the TTS chip, so there weren't enough holes in the breadboard space to accommodate one end of the chip, and their traces are fragile where they suggest the modification.
We set out to design our own shield based on what we did and did not like about the Sparkfun unit.
Well, we got scooped.
The guys at Droidbuilder built a better mousetrap, er, TTS Speakjet Shield. It has almost all the features we wanted in our shield, but also includes a hefty price tag. It is, however, a worthy unit, and has excellent tutorials. Enjoy the show!
Speakjet Users Guide
TTS 256 Datasheet