Speech output from a microcontroller

I am looking into generating speech output from
a small datalogger (approximately match box size).
Any advice on how to go about it? There will be a
memory card and the words come from a small fixed set,
so storage is not a problem.

Way back there was a speech synthesizer for the RCA1802
that only used a single digital output pin, but the
sound quality was really not very good. What I'm looking
for is something similar, but with a bit higher quality.

I'm planning to use one of ATMega devices, though that
probably does not make much difference.
--
Pertti
.