For online rehearsal aids, see here.
Musical Terms: Glossary of Common Terms
Pronunciation Guides
German
With Audio
Alphabet
Diphthongs and Consonant Pairs
Dangers to Avoid
Italian
Vowels
Consonants
Double Consonants, Diphthongs, Tripthongs, etc.
Word Stress
Latin
American Guild of Organists – Pronunciation of Church Latin
Singing Technique
eHow.com: How to Do Breathing Exercises
Voicetraining @ The Vocalist
Vocal tips, at: https://www.chorusonline.com/vocaltipscvt
Music Theory
Music Notes – Note reading, intervals and scales
Music Theory Net – from basic theory to advanced chord analysis
Practice Spot
Practice
Big Ears – the Original Online Ear Training
Teoria.com – excellent interactive and fun exercises
Thanks to The Singapore Symphony Chorus website for these links.