Two launcher activities

You need to specify which activity is the default one by adding the following line to your intent-filter:

<category android:name="android.intent.category.DEFAULT"/>

Insert this in the default activity and keep the rest. Then it should work.

You may also want to add a different icon to your 2nd activity with the attribute android:icon="@drawable/myothericon"

Add <action> items with android:name attributes defined to both intent filters:

<application
    android:name=".MyApp"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name" >

    <!-- work order activity -->
    <activity
        android:name=".app.WorkOrderActivity"
        android:label="@string/work_order"
        android:taskAffinity="com.package.task_for_work_order_activity" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <action android:name=".app.WorkOrderActivity"/>
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

    <!-- inventory activity -->
    <activity
        android:name=".app.InventoryActivity"
        android:label="@string/inventory"
        android:taskAffinity="com.package.task_for_inventory_activity" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <action android:name=".app.InventoryActivity"/>
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>