Hammond Music Service
They provide nominally priced tapes and CDs to help chorus members learn their parts
Cyberbass
Innovative Learning for Choral Singers
They provide MIDI files of voice parts to facilitate learning
Classic Cat
Classic Cat is a directory with links to over 2800 free to download classical performances on the internet, sorted by composer and work.
eClassical.com
This is an inexpensive service to download classical music. Most selections are only $0.99 and they have deals from time to time that they communicate through newsletters. They claim to have the largest collection of classical music for downloading.
Emusic.com
This is an inexpensive subscription service to download music. $9.99 per month allows you to download 40 songs. Their selections are pretty good.
I-Tunes
This is a subscription service to download music. Most songs are $0.99 and they discount full CDs.
vocalist.org.uk
An excellent web site for all types of singers. It has many useful tips, exercises, vocal health issues, software, sight reading help.