This well-organized site offers information on composers, musical forms, instruments, and other details on the classical period as well as other musical periods. (
http://library.thinkquest.org/27110/noframes/homepage.html
)
This site includes a timeline of the development of the symphony, biographies of important composers, sound files of their works (on piano), and lots more. It also reviews sonata form, a prominent feature of classical-period symphonies. (
http://library.thinkquest.org/22673/
)
This is a very complete site with biographical information, portraits of Mozart and his family, and a full list of his music compositions. (
http://www.mozartproject.org/
)
This beautiful site includes wonderful sound files of Mozart's music along with information on his life and his compositions. (
http://www.studio-mozart.com/Mozart/index.htm
)