Randall Davis mentioned several good sites and tools that I will simply list here--
EZ slang site:
has short audio with slang expressions. One thing he cautioned is that 20 sec. to 4 min. is about the max that you can do with audio without other kinds of support (e.g., photos or video or script). Listening is just plain hard, as I learned when testing Chinese EFL teachers years ago--they were scoring 80-90% on the practice TOEFL grammar, and 10-18% on the listening part.
Questions for student discussion/interviews by Randall Davis:
This is a great site also for students to use as TOPICS for making their own video projects.
Here are some of my experiences with Audacity, which I have begun to feel is workable on the Mac (OS 10.3 or 10.4):
Open Audacity, hit Record button. Click Yellow >Stop button when finished.
Select >Export as...mp3 for smallest file size.
You will need the LameLib plug-in to export to mp3, which is accepted by most players, including RealPlayer and QuickTime, but not Windows Media when you are in a Mac. (LameLib can be found on a number of Apple sites, I believe--google it.) I assume the PC version of Audacity exports to .wmv files.
You can also play the Audacity file while recording it in WireTap, which creates a much smaller .aiff (QT) file.
For a tutorial in using Audacity to respond to student writing:
PC Tutorial - http://www.daniel.uklinux.net/tutorial/
MAC tutorial - http://altec.colorado.edu/howto/audacity/aud_hlp01.shtml