The only thing that worked for me was downloading the mysql-connector-java-5.0.8-bin.jar directly from the MySQL website:
http://dev.mysql.com/downloads/connector/j/3.1.html
Then if you're using Eclipse paste this mysql-connector-java-5.0.8-bin.jar in the WEB-INF lib folder
If doesn't works try with any of the solutions posted in this link:
http://javarevisited.blogspot.com/2012/03/jdbc-javalangclassnotfoundexception.html
