Wim gave an introductory presentation of Asterisk at the June 2004 meeting of the FVLUG. Presentation is available at: http://www.nyetwork.org/fvlug/FVLUG%20-%20Asterisk.htm
Example configuration files
Music On Hold
If you want to enable Music On Hold, you can't use Debian's mpg123 package. Doing an 'apt-get install mpg123' will actually install mpg321 instead. So, you'll need to remove mpg321 and instead compile mpg123 from source, do a 'make install', then symlink /usr/local/bin/mpg123 to /usr/bin/mpg123 so that Asterisk can find it.
Dealing with Echo