Here's a virtual online piano to help you find the right note.
Music Ed Ted's website
Various topics on how to develop and improve your voice for achieving closer harmony in barbershop. It's the next best thing to having Jay permanently on hand in your home!
The British Voice Association - the BVA's remit is the encouragement of a healthy voice, vocal skills and communication in such areas as the performing arts, business and industry, medicine and education.
The Musical Intervals Tutor - an online study aid to learning the sounds of the basic music intervals from minor second to perfect octave.
Primarily A Cappella (a US site) - improve your singing voice. Vocal instruction for singers.