PODCASTS were once the realm of computer geeks who took great pleasure in being able to download the few, mundane audio diaries available on the internet. But Ricky Gervais has consigned that image to the scrapheap this week with the runaway success of his online audio show.

Podcasts - audio files that can be downloaded and listened to on computers or portable MP3 players - have exploded in popularity.

The first series of The Ricky Gervais Show was made available free through The Guardian's website and was downloaded 4.5 million times - enough to get it into the Guinness Book Of World Records as the most popular podcast to date.

Podcasts are cheap and easy to make, and big guns like the BBC are now making their radio programmes available. So far, most are free. But Gervais will be testing the public's willingness to pay for the service by charging 95p per episode for the next series of his show. It is by far the most high-profile show to begin charging, although The Times sells Pounds 6.95 monthly subscriptions for a reading of its main stories and radio station LBC charges Pounds 2.50 for access to its back catalogue of old shows.

But there are plenty of free shows available. Here is our guide to the best of them, and how podcast virgins can join in the fun.

What is a Podcast?

A PODCAST is simply an audio program that is distributed over the internet, although the term has been expanded to cover videos. It combines the words "iPod" and "broadcasting", but this term can be misleading because they do not specifically require an iPod - any portable MP3 player or PC will do.

They are also not technically broadcasts.

Podcasts vary greatly - from amateur recordings made in bedrooms to repeats of BBC radio shows.

Making your own

ANYONE can make a podcast, which explains in part their huge popularity. All you need is a microphone and headphones to connect to your computer.

Then, download some audio recording software such as Audacity or iPodcast Producer.

Record your show, and the software will help you edit it and save it as an MP3. You can then post it onto your website if you have one, or publish it through websites such as Ourmedia.org, Audioblog.com or Liberated Syndication.

Download sites

DOWNLOAD some podcasting software onto your computer, either at Apple's iTunes music store or websites such as Ipodder.com.