Internet Music resources are mostly oriented toward 'popular' musics. These links provide a broad view of what's available:
WWW Music Resources
Netlink Music Resources
WWW of Music
A number of specific sites:
The Great Composers
via classicalmus.com (biographies and recommended recordings)
Classical Music on the Net
(Dr. Douglas Bell)
Classical Music FAQ
Early Music: archives of EARLYM-L and rec.music.early
Music Research Information Services
(CAIRSS database of music research literature --hit <ENTER> at the TS> prompt, type library at the 'enter application' request, and choose Local Databases from the Library menu)
CDs via the Internet
Reviews of Online Music Stores