For a quick intro, just tune to di.fm's trance channel. They have a lot of great trance radio shows; Global DJ Broadcast with Markus Schulz, A State of Trance with Armin Van Buuren, the aforementioned Trance Around The World, Global Trance Grooves with John 00 Fleming, etc.
For easily downloadable podcasts, Sander van Doorn's Identity (although he's leaning more electro these days), The Gareth Emery Podcast, and Global Trance Grooves are good ones.
I second this. di.fm is playing for about half my work day, and often when I'm at home too. I love the Trance and Vocal Trance channels, with forays into EuroClub, DubStep and Chillout Dreams.
For easily downloadable podcasts, Sander van Doorn's Identity (although he's leaning more electro these days), The Gareth Emery Podcast, and Global Trance Grooves are good ones.