The Maven Linkcheck Plugin allows you to generate a Linkcheck report of your documentation generated by the Maven Site Plugin.
You need to configure the reporting section in your POM like other Maven reporting plugins, i.e.:
<project>
  ...
  <reporting>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-linkcheck-plugin</artifactId>
        <version>1.2</version>
        <configuration>
          ...
        </configuration>
      </plugin>
    </plugins>
  </reporting>
  ...
</project>Here is a simple report:

The Linkcheck Plugin can be put into a project's pom.xml as follows:
<project>
  ...
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-linkcheck-plugin</artifactId>
        <version>1.2</version>
        <configuration>
          ...
        </configuration>
      </plugin>
    </plugins>
  </build>
  ...
</project>In this case, no report will be created, but the linkcheck files will be created in the target/linkcheck directory.
If you want to see a real life configuration you can have a look at the POM for the Maven site. There is a profile near the end called linkcheck.