Other
The Metropolitan Opera: Met History
Read about the history of the Metropolitan Opera. Content includes an image database of every performance since 1883, as well as a timeline of sights and sounds from the opera through the ages.
Naxos Digital Services
Naxos Digital Services: A to Z of Opera
Use the left navigation to access a solid history of opera as developed in various countries. You can also find synopses of opera stories, full opera libretti, and an index of opera composer's works.
Other
The Aria Database
The searchable Aria Database features over 1,200 arias from 170 operas by 60 composers. It includes lyrics, translations, synopses of operas, and MIDI files.
PBS
Wnet (New York): Opera Primer
Get to know more about opera with this well written website. Many people unfamiliar with opera can be intimidated by it or even think it is boring. This site will show you just what an opera is and maybe even convince to become a fan.