Q. What is podfic? A. Fanfic, read out loud. See here.
Q. What is Tolkien podfic? A. Go on, have a guess. Oh, all right then - Tolkien fanfic, read out loud.
Q. Why? A. Because it's nifty.
Q. Entirely convincing argument. How do I do it? A. You'll need some recording software (don't worry, there's free software out there, e.g. Audacity) and a microphone. Also, a quiet room, a spare few hours, and a big glass of water.
Q. Is it hard to do? A. There are some great tutorials out there. Take a look here, for starters. If you're using Audacity, I really recommend these tutorials. podfic_tips is a friendly and well-managed community where you can get advice.
Q. How do I post? What do I post? A. Upload your file (to an audio archive like Jinjurly's, or a site like Megaupload, or to your own site), then post the link. Tag your post with some identifying features, such as character, genre, Age, etc. Mature content is fine, but LABEL it accordingly. Include a link to the text too: some people like to read along. And say how big the file is.
Q. I don't write fanfic, but I'd like to read some out. Can I play too? A. Absolutely! But get the author's permission first.
Q. And it's really that simple? A. Honestly, it is.