I'm into this stuff big time. For those who aren't exactly aware, don't confuse it with audio books (which is how I did experience the full Harry Potter series, though). Audio books you have one person literally reading the book to you, though they will often put on different voices/accents when speaking as different characters.

But no, "radio theater" is a full cast production, an adaptation of the original story. Well, of those that are based on books, some radio theater pieces are original productions themselves, they're written that way. So we're talking multiple actors, sound effects, music, the whole deal. See I'm already a huge mystery fan, particularly the classics from Agatha Christie and Sherlock Holmes, and there are TONS of those stories done as radio plays. And of course (luckily) so many of them that are out there on the shelves in CD packets have been ripped and are online downloadable in mp3 form. I will most oftem load them up on my mp3 player and listen to some as I first get into bed at night (always takes me forever to get to sleep anyway).

Of course the BBC is pretty much the largest producer of this kind of thing.

As far as material gettable from torrents, some of the usual suspects (like Mininova, etc) do have an assortment, but I found a torrent site several months back that specializes in radio plays (well and all things spoken word, really).

http://radioarchive.cc/index.php

good stuff