Big Finish currently have the first episode of The Phantom of the Opera available for free via their podcast feed. That is episode one, in full, for free.
You can get the MP3 directly here or via the podcast RSS feed here, or via the iTunes store here.
From the Big Finish site:
"We at Big Finish are very proud of our full-cast audio adaptation of Gaston Leroux's classic tale 'The Phantom Of The Opera' and we'd like more people to discover its thrills and chills for themselves. The production stars Anna Massey, Alexander Siddig, James D'Arcy and Peter Guinness, and has been transmitted on BBC Radio 7 where it won instant acclaim and garnered five star reviews from many web sites and periodicals. However, some people have confused this adaptation of the novel with the musical of the same name. So, in the hope of dispelling this myth once and for all, we're offering the entire first episode for free!"
I did the sound design/editing and mixed the whole thing. More info on the whole project is available here: http://phantomaudio.co.uk/