The Gong project is a free open source tool enabling real-time and asyncronous audio discussion. It combines the power of online discussion with the elements of sound. Profound oral contributions to the class environment will no longer fade with the passing of time but can now be recorded and archived on the board for future recall. Use of this tool by educators, like most online tools, are primarily limited by our own creativity. It is easy to see the benefits of this tool across many disciplines, especially language courses. If you are an educator, talk with your tech person about implementing the system at your school. Once it is implemented it is quite easy to use as long as you have a microphone and speakers of course.
From The Gong site:
Gong is a free system for voice communication on the Web. It allows groups of people such as students and teachers to participate in discussion groups using their computers, using both synchronous (real-time) and asynchronous chat. It is commonly used by schools and universities for providing a 'voice board' for teaching purposes.
For more about the Gong Project, check out the website: http://gong.ust.hk/