Use maven-archetype-webapp to start a simple webapp maven project. The command is as follows
mvn archetype:create -DgroupId=[your project's group id] -DartifactId=[your project's artifact id] -DarchetypeArtifactId=maven-archetype-portlet
This would then create a maven project.
. |-- src | `-- main | `-- java | |-- [your project's package] | | `-- MyPortal.java | |-- jetspeed | | `-- web.xml | |-- resources | |-- webapp | | |-- WEB-INF | | | |-- tld | | | | `-- portlet.tld | | | |-- portlet.xml | | | `-- web.xml | | |-- help.jsp | | |-- maximized.jsp | | `-- normal.jsp | `-- index.jsp `-- pom.xml