<?xml version="1.0"?>
<config>
    <modules>
        <TM_Newarrivals>
            <active>true</active>
            <codePool>local</codePool>
        </TM_Newarrivals>
    </modules>
</config>

<?xml version="1.0"?>
<config>
    <modules>
        <TM_Newarrivals>
            <version>0.0.1</version>
        </TM_Newarrivals>
    </modules>
    <global>
        <blocks>
            <tm_newarrivals>
                <class>TM_Newarrivals_Block</class>
            </tm_newarrivals>
        </blocks>
    </global>
</config>

<?php
class TM_Newarrivals_Block_Lists extends Mage_Catalog_Block_Product_List
{
    protected function _getProductCollection()
    {
        // CODE TO LOAD TWO DIFFERENT CATEGORIES
        die("HERE");
    }
}

<newarrivals_layout>
    <reference name="content">
        <block type="tm_newarrivals/lists" name="newarrivals_lists" as="newarrivals_lists" template="tm/newarrivals/lists.phtml">
            <action method="setCategoryIds">
                <category_ids>5,6</category_id>
            </action>
        </block>
    </reference>
</newarrivals_layout>

<catalog_category_layered>
    <reference name="root">
        <action method="setTemplate">
            <template>page/2columns-left-filter-top.phtml</template>
        </action>
    </reference>
    <reference name="head">
        <action method="addItem">
            <type>skin_css</type>
            <script>css/responsive-catalog.css</script>
        </action>
    </reference>
    <reference name="mana.catalog.leftnav">
        <action method="setData">
            <instruction>hide_material</instruction>
            <value>1</value>
        </action>
    </reference>
</catalog_category_layered>

{{block type="catalog/product_list" category_id="2"  template="tm/newarrivals/lists.phtml"}}