http://www.cs.cmu.edu/afs/cs.cmu.edu/user/jdg/www/music_classical_pgh.html
This site is a comprehensive database of Classical Music Organizations and Series in Pittsburgh, Pennsylvania and includes schedules, contact details, information on various venues and much more. It's an excellent site for residents searching for concert events. Some of the organizations included are the Bach Choir of Pittsburgh, Bellefield Singers, Carnegie Mellon Music Department, Civic Light Opera, Mendelssohn Choir, Mercedes Great Performers Series, Pittsburgh Opera, and the Pittsburgh Symphony Orchestra.