maven-archetype-plugin is an archetype which generates a sample Maven plugin:
project
|-- pom.xml
`-- src
|-- main
| `-- java
| `-- $package
| `-- MyMojo.java
|-- test
| |-- java
| | `-- $package
| │ `-- MyMojoTest.java
| `-- resources
| `-- project-to-test
| `-- pom.xml
`-- it
|-- simple-it
| |-- pom.xml
| `-- verify.groovy
`-- settings.xml