The University of California, Berkeley is offering free audio courses and lectures through iTunes. If you don't have iTunes software installed you need to download it for free. Some disciplines have lots of courses and some have very few. Each course consists of a series of audio files, one for each class lecture and are usually about 45 - 50 minutes long.
How to get free audio courses:
Visit the Berkekey on iTunes site. If you alrady have iTunes you can click on the link and browse the free course selections. If you don't have iTunes you will need to download and install the free software.
The free course are available to anyone that can run the free iTunes software. There are versions for Mac and Windows.
What are risks in accessing the free audio couses?:
Your main risk, if you don't already have iTunes, is being tempted to visit the Apple iTunes store and actually pay for content.