Podcasting became a big craze in 2005, but most people believe this is more than a passing fad.
A "podcast" as it is today did not exist until about September of 2004. This is when various technologies came together for the first time to allow automatic delivery of syndicated audio content on the internet.
Instead of streamed audio that can be found on many internet radio stations, like SecondShifters.com, podcasting allows for the automatic download of whole MP3 audio files via a subscription.
It started as web journalers (aka bloggers) found ways to distribute their journals and put audio in them. This is known as audioblogging.
The internet is not just a text based place. Audio and video are as key to information as text is. So it did not take long before people were placing graphics, speech, music, and video on their blogs. Thus audioblogging and videoblogging (aka vlogging) were born.
When "real simple syndication" (RSS) was added to the programs that made blogging possible, it meant anyone could subscribe to a blog that caught their fancy. A news reader or aggregator program is all that is needed to subscribe to these syndicated feeds.
Dave Winer added the idea of "enclosures" to RSS. This added the ability to know exactly where an audio or video file could be found and downloaded from. As soon as news aggregators were programmed to automatically download the enclosed files and save them on the reader's computer, or perhaps to a portable media player, podcasting was born.
Adam Curry is credited with being one of the first to marry all of the technologies together. He had an audio blog and wanted a way to get the sound files directly onto his iPod player. He wrote a script to do this from his RSS feed and started a revolution. He's also credited with coining the term "podcast" as a hybrid of iPod and broadcast.
However, though iPods are the defacto standard media players, you do not need to have an iPod to listen to a podcast. Most podcasts are MP3 audio files, so as long as your computer can play MP3, or if you have any type of portable MP3 player, you can listen to a podcast. In fact, you don't even need a news aggregator, nor do you need iTunes. These programs, often called "podcatchers", just make getting podcasts easier.
Moreover, people are making podcasts about anything. There are podcasts covering news, talk, music, technology, comedy, audio books, storytelling, and every type of hobby. There are many reasons for this, just as there are many types of blogs. As more people learn about podcasting, it will become more diverse and even easier to subscribe.