I wanted to read Lucy Prebble's Enron, so I requested it from the library, but I accidentally requested not the script, but the recording of the play by LA Theatre Works.
And I'm really glad I did! After listening to the play with a stellar cast, I went to the interwebs to find out more about what I'd gotten.
And it turns out LA Theatre Works has been making audio recordings of plays for 25 years. They stream a weekly broadcast free of charge, and have a library of over 400 recordings of plays ranging from the Greeks to Shaw to Roberto Aguirre-Sacasa. You can buy downloads or CDs at their site, and I found over 40 titles available in the SF Public Library system on CD.
A fantastic resource for theater folks of all stripes.
Check 'em out here.