I use Amazon s3 for Podcast hosting. Not just podcast hosting, but also for giving “lead magnets” to people who optin to the email lists.
Because it is most flexible. I used to use other dedicated podcast hosting plans, but when I started to do multiple podcasts they charged me by the amount of feeds. When I started to use Amazon s3, I could use it for as many podcasts as I wanted, as well as for video, pdf, ad even making resource sites.
For example you can check out http://resources.mikesblog.com – this is where I put the images and other frequently asked downloadable items for people to access.
Why not just put it in WordPress Media files?
This is a common question – sure you can put mp3 files and pdfs in the media section of wordpress. But the hosting companies are not built for you to put these larger static files. They do not need to put extra strain on your web server – if you get a big spike of traffic for taht podcast or that blog with the pdf, it may take down your blog.
By having the media files stored on a separate server that is cloud based like Amazon s3, then it scales up as you need it and keeps your website (web server) totally separate from that spike of download.
It is a bit more technical though, but that also means it is much more flexible.