These resources may help you to find information regarding music vocabulary, theory, history, recording details, and instrumentation.
The Open University: Music Resources - contains links to information about music history, musician biographies, music genres, and instruments.
AllMusic - a comprehensive and in-depth resource for finding out more about the albums, bands, musicians and songs you love.
Discogs - a comprehensive music database and marketplace
Songfacts: a searchable database of song information where you can find out the stories behind the songs, get the lyrics, and watch the videos.
AZLyrics - Lyrics!
Ultimate Music Database: (Almost) Complete Database of Pop Music
Review publications such as Pitchfork, Rolling Stone, XXL might be useful for finding information on artists, bands, albums, and genres.