Some resources that I've found

[n00bsWithBoobs]

I really liked these places for the possibilities of what is achievable:

This gal on youtube is beautiful, 38 years old, and can slide from obviously masculine voice to amazing womanly voice. Look through her videos that discuss voice.

http://www.youtube.com/user/candiFLA

This was a good site a little off the beaten path. Quick and informative.

http://www.amberspace.net/voice.html#terms