The third annual Podcast and New Media Expo, formerly known as the Portable Media Expo, started today in Ontario, California and runs through the weekend. The event has become a favorite of podcasters and video creators from all over the world.

Keynote speakers at the conference this year include serial investor Howard Lindzon, investor in the CBS acquired video blog Wallstrip, Jim Louderback, CEO of Kevin Rose-affiliated Revision3 and Kent Nichols and Douglas Sarine of Ask A Ninja.

Podcasting News reports that you can keep an eye and an ear on the action at the Expo this year in a number of ways, including an official Twitter feed and audio interviews both live and rebroadcast from the surprisingly successful startup BlogTalkRadio (see our review of the service last month). Live BlogTalkRadio coverage will be provided by Guide to Podcasting John C. Havens and will will start tonight at 5:30 PST (12:30 AM GMT). Coverage kicks off with an interview with Paolo Tosolini of Microsoft on the value of corporate podcasting and new media production. The whole event schedule is here.

Technologies like podcasting, easy live broadcasting and Twitter have changed the conference experience forever; a conference full of specialists in the use of these technologies should be particularly interesting to watch from outside.