Here is a BBC programme narrated by Villazon, explaining the history and technical aspects of the tenor in Opera. It features a great number of fantastic singers, there's also a lot of information here about opera in general. A great introduction to opera, some lovely arias sung by fantastic singers. If anyone can explain opera and singing to the general public, it's Maestro Villazon.
Here's the whole of 'Werther' with Villazon. Available until later this evening. Search for Villazon on YouTube to find more.
If you want to sample some opera, here is the next of the Rosenblatt Recital Series.