I've been using Rhythmbox a lot lately. Its great for listening to music, but you can do more, like browse the Ubuntu One Music Store and buy music, or even listen to podcasts. There is a travel show I like to watch on public TV called Rick Steves' Europe. Browsing his website, I found he also has a weekly radio travel show. The link below graciously lists the XML podcast link, making it easy to cut and paste it into Rhythmbox....
... but many radio shows and hosts like Rudy Maxas' Travel World dont offer easy links like this. Instead, they direct you to a proprietary iTunes page. If you dont have iTunes, you're out of luck. Not anymore. A quick search on the Ubuntu Forums found me the Feed Flipper.
Plug in the itunes URL of the podcast feed you are interested in on this page:
Copy the highlighted blue web link and paste it into Rhythmbox when it asks for the URL of the new podcast you are trying to set up. Simple as that! Have fun! There are tons of podcasts allover the internet. From travel shows to linux shows to even learning a foreign language, you can certainly find a podcast to fill up a boring work day!