UUCUC Adult Choir
Choir Repertoire and Recordings
UU Musicians Network
Resources for UU musicians, go figure!
Music Theory Lessons/Exercises
Great site with valuable explanations and chances to test what you've learned.
A website with Midi tracks for just specific voice parts of great works. This link takes you to the page for the Brahms Requiem (movement 4 is "How Lovely Is Thy Dwelling Place").
The Singers Resource
Website with advice, articles, explanations, tips - you name it! I haven't thoroughly vetted this, but what I've seen seems valuable.
Ear Training Lessons/Exercises
Teoria is similar to MusicTheory.net in providing tutorials and then exercises.
A resource with phonetic spellings and tips for singing. It also has "How to pronounce Italian" and many other languages in PDF form.