For no particular reason I spent the evening added Trackback to my music database, so now when I mention something about one of my CDs in my LiveJournal, I can ping my music collection and a link to my LJ entry automagically appears on the page for the CD!Here's a recent example
And if/when LiveJournal eventually implements Trackback for journals, I'll be able to ping it directly instead of having to munge the URL.
Of course, I then went back through my journal and found only a handful of occasions when pinging my music collection was useful, but hey, it's the geekiness that counts.
(Hmm, is this a web first? A trackback-pingable music collection?)