My favorites utility for generating way-too-low spoken text is AudioX’s SayIt. You can tune the thing so low it’s just sounds. Sweet.
NOTE: the uncompressed source for the 1K speech-code is at the above link.
Both of these are based on Tiny Speech Synth (demoscene file, in c++)
MeSpeak is in-browser speech, in JS. Pretty good, far better than the above, but not as funky as the above. AWWWW.