Recent Update on CE/eBox Speech Synthesis: There is also a "student project" Win CE port of the free Espeak public domain speech synthesis program with a demo program available for the eBox and it is described in the Windows CE Academic course materials available from Microsoft. You can find it in Chapter 9 Section 4 of the second edition of the textbook. It generates a *.wav file from ASCII text and then uses the Playsound API to play the wave file in another process. You can just download the Espeak CE version tts.exe file over the web using the URLs in the book along with the Speak CE demo subproject (on book's CDROM example design files) and should not need to rebuild the TTS engine, if you are happy with the default voice setup. There is also a speech sample embedded in the PowerPoint slides that go with the textbook that was produced on the eBox.
Here is the link for the textbook:
http://www.facultyresourcecenter.com/curriculum/pfv.aspx?ID=7435