This screencast introduces the exclamation mark and reviews appropriate and inappropriate uses.
Source: Kathryn Reilly
For more information regarding interjections and exclamation marks, try
http://www.englishclub.com/grammar/interjections.htm
For some simple practice in selecting when to use exclamation marks, try
http://www.studyzone.org/testprep/ela4/g/exclamationmarksp.cfm
Source: see above
