Note: From Ubuntu 13.04 (Raring) onwards, tunesviewer is available in the repositories, and so can be installed with a simple sudo apt-get install tunesviewer.

For downloading itunes podcasts and itunes University material, the easiest way is to use TunesViewer instead of hpodder. The former program cleverly masks your user agent and appears to apples's site as the itunes program and so is able to parse all the itunes urls; once installed, you can even click an itunes link in Firefox and it will open in TunesViewer.

TunesViewer 1.5.2 can be downloaded from sourceforge and is a .deb file so is easily installed by double-clicking and selecting install in Software Centre; it has very few dependencies and is a much lighter-weight program than iTunes. You can set the location of your download folder from edit > preferences and then you should click the box to set TunesViewer as 'default opener', so any browser links will open in it. You download your podcasts by right clicking the files in the bottom tab of the program or the "free" link above, or you can just play them if you want with an external application such as rhythmbox, which it has been tested with.

There are some great itunes U courses available (the first screenshot shows the one you want) and if you click the box in the far left hand corner of the program interface you can select to search for itunes U or regular itunes podcasts. You can of course manually copy an url into the program and load it up.

TunesViewer is the only decent way to access the itunes U or podcast pages of apple.com on Linux without installing iTunes in wine. You don't need to know a link before hand and you can just start the program, and from the itunes U homepage, you can go to all the other itunes podcast pages. It's a great program that I use a lot!