I may have mentioned KavaSoft on this site before, but the one-person company just released an update to their iTunes Catalog software which dramatically improves their online cataloging features - making it appear just as you were viewing your iTunes library, and it browses your personal music as if you were at the iTunes music store.If you have a Web site, or just want to poke around with one of the very best independent software applications for the Mac I've ever seen, check it out. And it handles large libraries just fine, as you can tell with my 3,400+ song, 18 days, 28.5 Gig demo.
http://www.louisgray.com/music/