Syslog-ng best thing since sliced bread
I really recommend this to any sys admins who have to dynamically deal with log output. I use it in a manufacturing facility to split log streams from many log clients into separate files based on hostname and other test system data. The ability to send the log stream to the stdin of a program is a feature you just can't find anywhere else.
A sophisticated command line based file transfer program.
A ballroom music player.