Resources for Singers

News:
Operabase
All About Opera
Playbill
Playbill Arts
OperaGlass
Opera News

Reference Resources:

Ithaca College Music Library
Naxos Music Library
Grove Music On-line
The Business of Singing Worldcat.org
Internet Archive (including "Wayback Machine")
Catalogues of composers' works
Karadar Classical Music
The Scenes Database
The Aria Database  

Music and Scores:
IMSLP International Music Scores Library
Classical Vocal Reprints Educational Music Services  

Scripts, Monologues, and Libretti:
Simply Scripts
Opera-L
Karadar Classical Music
Monologue Archive
Audition Preparation
Musical Theater Audition  

Translations:
Babelfish
Rec Music
The Aria Database

Local Opera Companies:
Syracuse Opera
Tri-Cities Opera

Summer and Young Artist Program Information:
YAP Tracker

Professional Affiliations:
Opera America
Musical America
Classical Singer
National Association of Teachers of Singing

Choral Music Resources:
Choral Public Domain Library 
Musica International Virtual Choral Library

Early and Sacred Music:
Goldberg Early Music Portal GFHandel.org 
Bach Cantatas Website
Early Music FAQ CyberHymnal
 
Musical Theater:
Playbill
Musical Theatre International
R&H Theatricals
The Guide to Musical Theatre
British Musical Theatre
Stephen Sondheim Reference Guide
Gilbert & Sullivan Archive
Musical Theater Audition
Musicals101
Backstage