I just discovered MUSIClassical.com. It has a section called CLASSICALmanacTM that lists major classical-music events for every day of the year. Here's a sampling of what's listed for today, January 11:
1642 Birth of German organist and composer Johann Friedrich ALBERTI in Tönning, Thuningen.
1754 FP of second version Jean-Philippe Rameau's opera Castor and Pollux in Paris at the Palais Royal Opéra. (I think FP means "first performance.")
1801 Death of Italian composer Domenico Cimarosa, in Venice at age 51. b-Aversa, 17 DEC 1749.
1837 Death of Irish pianist and composer John Field in Moscow, on tour. b-Dublin, 1782.
1843 Death of Francis Scott Key, composer of Star Spangled Banner, at age 63.
1856 Birth of Norwegian composer Christian SINDING in Kongsberg, Norway. d-Oslo, 3 DEC 1941.
1895 FP of Johannes Brahms's Clarinet Sonata, Op. 120, no. 1. Richard Muhlfeld, clarinet and Brahms at piano, in Vienna.
1906 Birth of composer Johannes Paul THILMAN. d-1973.
1906 FP of S. Rachmaninoff's two one-act operas The Miserly Knight and Francesca da Rimini in Moscow.
1909 Birth of composer Gunnar Johnsen BERG.
1910 Birth of American conductor Izler SOLOMON in St. Paul, MN.
1925 FP of Aaron Copland's Symphony for Organ and Orchestra, at Aeolian Hall in NYC. New York Symphony, Walter Damrosch conducting. Nadia Boulanger was the soloist.
1940 FP of Prokofiev's ballet Romeo and Juliet in Leningrad.
Et cetera. The site also includes links to composer information pages (the names in all-caps are links on the page) and CD info (amazon.com links).