Anyone who listens to MP3 should consider downloading the
MusicBrainz tagger. It searches your MP3 files and compares the information versus their huge user-modified database. If your tags are incorrect they fix them. The program takes some time to figure out, but once I got the idea it's really a great piece of software for getting your MP3's in order.
The use of MusicBrainz was prompted by
Audioscrobbler, a plugin that keeps track of all the songs you listen to and then makes reccomendations based on others listening habits. I'm not sure that AudioScrobbler is allowing any new users to sign up at the moment, though if they are it's worthwhile and a fun way to find new music.
Last, and this has nothing to do with music. If you don't have a
del.icio.us account, get one. It's a social bookmark program that allows you to bookmark webpages of interest in a public place. Instead of using a folder hierarchy, del.icio.us uses tags that allow you to identify a link in multiple categories. All the links on the right side of this page are kept on del.icio.us and then fed onto this page. I've also found it incredibly useful for work where it allows me to easily organize information that I plan to use for future stories. When you sign up you get a little button to put on your toolbar that allows you to bookmark any page you're on very easily. Go sign up.
Update (6/26/05): As I was going back through old entries adding categories, I realized this was really a Newly Discovered, so I have adjusted it accordingly.