A podcast hosting service is like any other web hosting service but with one big difference - the podcasts (like mp3, mov, wmv) are much larger in size than the standard html pages or the web images so you need larger storage space. Secondly, if your podcast show is popular and more listeners subscribe, you will consume a huge amount of bandwidth as people download your creation to their iPod or hard disk. Infact, if you are not careful in choosing your podcast hosting provider, the situation would be akin to getting slashdotted and digged multiple times in a day. Either your site would go offline or you'll see many more zeroes added to your bandwidth bills.
Related: Download Podsafe Music (MP3)
It is therefore advisable to have a dedicated podcast host and then use your existing ISP or web host to just link to them. Doing so will not have any effect on the bandwidth of your current host since the content will be streamed/downloaded from the Podcast hosting servers. On an average, a 30 minute talk show encoded at 64 kbps will have a file size of 15 MB. So if you host a daily show with 10 subscribers, you are likely to consume 5 GB bandwidth and would require half GB of space per month.
Here we do a quick comparison of features, pricing models, etc offered by the most popular media hosting companies where you can upload your podcasts or video blogs.
Update: You can host podcasts on Google Drive for free.
Libsyn: The most popular audio-video hosting service, Liberated Syndication offer offers various plans with monthly price ranging from $5.00 to $30.00 depending on the server storage space that you want to buy per month. Libsyn offers unlimited bandwidth. You can try the libsyn service without signing up or sharing your credit card details by using the libsyn sandbox account (user: sandbox, password: sandbox). Each month your files are archived and the monthly storage quota is refreshed. As an example, if you upload a 25 MB mp3 file today, 30 days from now it will be archived and 25 MB of available space will be restored to your account.
LibsynPro: This is more like the business version of Libsyn inclined for non-technical users to manage their podcast feeds or for people who like to manage multiple podcasts from one place. Media files as large as 2 GB can be uploaded via the web interface or through FTP. Prices of Libsyn Pro aren't available yet but they do guarantee a 99.9% uptime.
HipCast: Earlier known as audioblog.com, Hipcast provides podcast hosting services as well as the tools required for creating podcasts and video blogs from scratch. The have four different plans with unmetered bandwidth plans. The cheapest $10/month offers 500MB of space while $50 plan offers 5GB of server space. They also have an interesting unlimited storage plan at $4.95/mo where you get unmetered Storage but 5 GB of Transfer per month. Additional transfer would cost you $1.95/GB. 7 day trial available.
GoDaddy: The name synonymous with Domain Name registrations, GoDaddy, has just made an entry in the mp3 hosting business. They have three quick podcast plans but neither of them offers unlimited bandwidth or unlimited storage. For $5/month, you get 1GB of storage with 100 GB bandwidth. while the $20 plan gives 10 GB disk space for 500 gigabytes of data transfer. So you will have to do the calculation youself based on the average size of your podcast files and the number of suscribers you have. If some of audio show is a viral hit, you are bound to exceed the bandwidth limit. There's no mention of additional bandwidth charges.
OurMedia: A free hosting service for your audio and video files with unlimited bandwidth and unlimited disk space. Your podcasts and vidcast files are uploaded to the Internet Archive servers [archive.org] under the Creative Commons license. You specify the license details at the time of uploading so that so that others will know what they may (or may not) do with with your audio. The content should not include pornography.
Odeo Studio: Odeo has tools to record podcasts or store them for sharing. They will host your podcasts for free thought there's a 50mb limit per uploaded file. However, there is no limit to how many files you can upload. The only downside is that if people hear the podcast outside the Odeo Flash Audio player, they will have to hear a short Odeo commercial. There are no limits othewise and Odeo is a very easy to use service from the guys who created Blogger. Does not support video. [studio.odeo.com] *Update: Odeo Podcast Studio is no longer available.
Conclusion: To choose the right podcast host, it really depends on how may podcasts you want to produce per month, how big they will be and what kind of subscriber base you are expecting for your shows. All the services mentioned above are reliable enough with powerful infrastructure. Libsyn has a very strong community around it in the form of forums so you are likely to get answers to your queries very quickly. I would suggest people to stick with plans that offer unlimited bandwidth because you never know when you produce that hit content which take the entire web by storm. You won't like to go bankrupt just after delivering that masterpiece.
If you don't mind a 3 second commercial, stick with Odeo. If you are not worried about people reusing your content, try OurMedia. Else Libsyn is you destination.
Update: Free MP3 Podcast Hosting at Blip.TV