I've covered the reasons for doing so in various posts about self-programming. The basic one is that you are programming your mind all the time anyway, you might as well fill it with something useful...
There is a simple way (and free, except for your time and effort) to podcast.
1) Create the podcast. (I used a Text-To-Speech voice and a text editor. Windows XP has some free voices, as do others. NotePad Light is my preferred text editor - a free download.)
2) Biggest expense is usually covering the tab of bandwidth. The Internet Archive comes to your rescue, since they are looking to create a digital library of cultural artifacts - as long as you own and can make available your audio work under a Creative Commons license (nobody can make a dime unless you do), they cover the bandwidth of all downloading. Upload your podcast.
3) Create a blog on Blogger and link the title of your blog entry directly to the podcast. (Other blogs may work - see next step below, I just prefer Blogger.)
4) Run your link through FeedBurner, who has a special page for Blogger patrons.
5) Promote your podcast through the various directories. (A lot of these are available through Feedburner, who also supplies you with statistics and other whatnot.)
And there you have it.
As I get time, I'll work up a podcast for Go Thunk Yourself series - it will have Go Thunk Yourself (currently available in audio via Lulu) and also I can put Haanel, Hill, and others up there as I convert them over to TTS files.
Nice way to surround yourself with audio to re-program your mind.
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Found that once works are published on Lulu, they have a fixed address so that you can link to them on a blog, burn that feed with feedburner, and then post your podcast to the various podcast directories. Of course, to be fair, they should all give credit and point to Lulu - as well as your storefront there - so they get the support their deserve.