Wordpress used to only come with one plugin by default (Hello Dolly), but now also comes with akismet (which is great, btw). If you look into the hello.php file you will see very quickly where the lyrics are put. You can substitute or add your own lines of text to be displayed.

Personally, I commented out the hello dolly lyrics and put in a list of 311's lyrical wisdom that I found online the other day. My initial thought was to use it as a traditional motd, but instead decided to use this list of 311 lyrics that I downloaded a while ago. (If you are the original compiler of this list, please let me know, and I will credit/link you.)

So if you are a 311 fan like me and you want to use the hello.php file that I'm using, just download it here (updated for wp2.5).

The next step i would like to take with this is to get this on the homepage. It looks to me like you'll just have to change the add_action commands to insert the text on the homepage instead of the admin pages. I found this page in the codex but changing admin_header to get_header and admin_footer to get_footer didn't seem to work. If you know how to do this, please comment or email me.