Mp3 players are pretty common nowadays. Not necessarily in the form of standalone devices, but integrated into smartphones that everyone seems to use nowadays.
While they are primarily used to play music, they can also be used to play podcasts and audiobooks. The best way to explain podcasts is to compare them to radio shows. Some hosts talk about certain topics, you listen to jingles, to music sometimes that is played during breaks.
Not all podcasts are like radio shows of course, some are like audio lessons, like university courses without the classes. And this is what I will be talking about now.
I found a great website that has three large lists of links to websites that offer podcasts that teach you something. That something is either a language, culture or university courses. It is up to you of course to decide what you want to learn and hear, just download all the podcasts you like and transfer them to your mp3 player.
All podcasts are encoded in mp3 format which makes it possible to have even large lessons take up just some megabytes.
Let us take a look at the three possibilities:
Languages: Links to podcasts that teach you 14 languages including German, French and Japanese. Most of the courses are for beginners, I suggest you read the explanation at the website that compiled the list before you download the podcasts.
University Courses: A compilation of links to colleges and universities (US) that offer free podcasts of some of their lectures. You find a wide variety of courses such as law and social sciences.
Culture: Many links to interesting podcasts and even audio texts. Concentrates on art, pop culture and media. Great.
Update: With the rise of smartphones and tablets came new opportunities. You can naturally transfer and listen to these podcasts on those devices as well. Basically, if it supports mp3, you are good to go.
Update 2: The Open Culture website has additional lists available now that you may want to browse through. This includes free audiobooks divided into fiction, poetry and non-fiction and a lot of other listings that you find in the top navigation toolbar and right sidebar.