Creating a Cron entry to start a program at a particular time?

[John Aldrich]

How do I create a CRON entry to, for example, start XMMS at
0600 and play a particular MP3 file (or KMP3 to do the
same)???
What I'm wanting is to do something similar to what I had
under Windows 98's Task Scheduler -- use my computer as an
alarm clock.
Thanks...