I like to have my computer write greetings and the like to me, like sentient supercomputers in bad sci-fi flicks (and computers running Novell Netware -- not that I'd associate Netware with sentience....) do. While I guess in these bleak times of rationalization and productivity maximization a stupid little toy like this seems trivial and unnecessary, I find that I'm in a much better mood to code if my computer helps me feel like a mad scientist tinkering with strange contraptions in the darkness of night, accompanied only by his trusty electric brain.
Here is the little piece of shell scripture I use to get it to do that (works in all Bourne shell derivates -- I use ksh, but you new-school bash users should find that it works with no modification). Put this in your .profile:
if [ $HOUR -lt 5 ] ; then
elif [ $HOUR -lt 12 ] ; then
elif [ $HOUR -lt 18 ] ; then
echo "Good $GREETING_TIME, $USER. Your wish is my command."