Sample Maven 3.0 Site Generation with Reports (parent POM). Uses Aggregation.

pom-fragment.xml

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-site-plugin</artifactId>
  <version>3.0</version>
  <configuration>
    <reportPlugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-project-info-reports-plugin</artifactId>
        <version>2.2</version>
      </plugin>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-javadoc-plugin</artifactId>
        <version>2.8</version>
        <reportSets>
          <reportSet>
            <id>aggregate</id>
            <reports>
              <report>aggregate</report>
            </reports>
          </reportSet>
        </reportSets>
      </plugin>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-jxr-plugin</artifactId>
        <version>2.3</version>
        <reportSets>
          <reportSet>
            <reports>
              <report>aggregate</report>
              <report>test-aggregate</report>
            </reports>
          </reportSet>
        </reportSets>
      </plugin>
      <plugin>
        <groupId>org.codehaus.mojo</groupId>
        <artifactId>javancss-maven-plugin</artifactId>
        <version>2.0</version>
      </plugin>
      <plugin>
        <groupId>org.codehaus.mojo</groupId>
        <artifactId>findbugs-maven-plugin</artifactId>
        <version>2.3.3</version>
      </plugin>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-surefire-report-plugin</artifactId>
        <version>2.11</version>
        <configuration>
          <aggregate>true</aggregate>
        </configuration>
        <reportSets>
          <reportSet>
            <reports>
              <report>failsafe-report-only</report>
              <report>report-only</report>
            </reports>
          </reportSet>
        </reportSets>
      </plugin>
    </reportPlugins>
  </configuration>
  <executions>
    <execution>
      <id>attach-descriptor</id>
      <goals>
        <goal>attach-descriptor</goal>
      </goals>
    </execution>
  </executions>
</plugin>