I used the Mac's speech ability and scriptability to make a quick talking clock. I ran this script and turned up my speakers and set all the clocks in the house with ease:
while [ 1 ];do z=`date +%S`;if [ `expr $z % 5` -eq 0 ];then say `date "+%l %M and %S seconds"`;fi;done
[crarko adds: I tested this, and it works as described. Note that this is bash shell syntax; if you use a different shell you may need to modify the script accordingly. I give it an A for cleverness.]

