I don't think there is such a ready-made "default" application present in JBoss. Assuming that u have a running setup of webconatiner-jboss 3.0.6, heres what u need to do:
1. Create a mytestweb.war folder in yr <jboss-home>\server\default\deploy folder. Note the .war extension to the folder. This is how you deploy exploded web apps.
2. edit yr web.xml if required.
3. assuming u have a mytest.jsp in <jboss-home>\server\default\deploy\mytestweb.war folder, u cd then access it as http://server:port/mytestweb/mytest.jsp