Great first stop for composer, genre, period, instrument information and more. Article bibliographies get you to the next step in your research. Includes Grove Music and other relevant titles.
Google Scholar can be a useful searching tool, particularly when it checks against the electronic full text holdings at FSU. This link requires you to log in with your FSU e-mail information-- but it's worth it!
This online resource includes several major encyclopedias, including the Enyclopedia of Popular Music (2009) and the Grove Dictionary of Music and Musicians (frequently updated).