Using a clean maven web-app.

Creating a new maven web-app:
mvn archetype:create -DgroupId=org.apache -DartifactId=shindig-app -DarchetypeArtifactId=maven-archetype-webapp
Configuring jetty:run plugin:
<plugin>
	<groupId>org.mortbay.jetty</groupId>
	<artifactId>maven-jetty-plugin</artifactId>
	<configuration>
		<tempDirectory>${basedir}/target/work</tempDirectory>
		<webApp>${basedir}/target/${finalName}.war</webApp>                    
		<contextPath>/</contextPath>
	</configuration>
</plugin>
Adding shindig as dependence:
<dependency>
        <groupId>org.apache.shindig</groupId>
        <artifactId>shindig-features</artifactId>
        <version>2.0.0</version>
</dependency>
<dependency>
	<groupId>org.apache.shindig</groupId>
	<artifactId>shindig-common</artifactId>
	<version>2.0.0</version>
</dependency>
<dependency>
	<groupId>org.apache.shindig</groupId>
	<artifactId>shindig-gadgets</artifactId>
	<version>2.0.0</version>
</dependency>
<dependency>
	<groupId>org.apache.shindig</groupId>
	<artifactId>shindig-social-api</artifactId>
	<version>2.0.0</version>
</dependency>
<dependency>
	<groupId>org.apache.shindig</groupId>
	<artifactId>shindig-extras</artifactId>
	<version>2.0.0</version>
</dependency>
Configuring web.xml:
<?xml version="1.0"?>
<web-app>

       - configuration -->
    <!-- If you have your own Guice module(s), put them here as a colon-separated -->
        
    <context-param>
        <param-name>guice-modules</param-name>
        <param-value>
            org.apache.shindig.common.PropertiesModule:
            org.apache.shindig.gadgets.DefaultGuiceModule:
            org.apache.shindig.gadgets.oauth.OAuthModule            
        </param-value>
    </context-param>

    <listener>
        <listener-class>org.apache.shindig.common.servlet.GuiceServletContextListener
        </listener-class>
    </listener>

    <!-- Render a Gadget -->
    <servlet>
        <servlet-name>xml-to-html</servlet-name>
        <servlet-class>
            org.apache.shindig.gadgets.servlet.GadgetRenderingServlet
        </servlet-class>
    </servlet>

    <!-- Proxy -->
    <servlet>
        <servlet-name>proxy</servlet-name>
        <servlet-class>
            org.apache.shindig.gadgets.servlet.ProxyServlet
    </servlet-class>
    </servlet>

    <servlet>
        <servlet-name>concat</servlet-name>
        <servlet-class>
            org.apache.shindig.gadgets.servlet.ConcatProxyServlet
    </servlet-class>
    </servlet>

    <!-- OAuth callback -->
    <servlet>
        <servlet-name>oauthCallback</servlet-name>
        <servlet-class>
            org.apache.shindig.gadgets.servlet.OAuthCallbackServlet
        </servlet-class>
    </servlet>

    <!-- Metadata RPC -->
    <servlet>
        <servlet-name>metadata</servlet-name>
        <servlet-class>
            org.apache.shindig.gadgets.servlet.RpcServlet
    </servlet-class>
    </servlet>

    <!-- javascript serving -->
    <servlet>
        <servlet-name>js</servlet-name>
        <servlet-class>org.apache.shindig.gadgets.servlet.JsServlet
        </servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>js</servlet-name>
        <url-pattern>/gadgets/js/*</url-pattern>
    </servlet-mapping>

    <servlet-mapping>
        <servlet-name>proxy</servlet-name>
        <url-pattern>/gadgets/proxy/*</url-pattern>
    </servlet-mapping>

    <servlet-mapping>
        <servlet-name>concat</servlet-name>
        <url-pattern>/gadgets/concat</url-pattern>
    </servlet-mapping>

    <servlet-mapping>
        <servlet-name>oauthCallback</servlet-name>
        <url-pattern>/gadgets/oauthcallback</url-pattern>
    </servlet-mapping>

    <servlet-mapping>
        <servlet-name>xml-to-html</servlet-name>
        <url-pattern>/gadgets/ifr</url-pattern>
    </servlet-mapping>

    <servlet-mapping>
        <servlet-name>metadata</servlet-name>
        <url-pattern>/gadgets/metadata</url-pattern>
    </servlet-mapping>
    
</web-app>

Trying:
mvn clean package jetty:run

Now you can navigate to http://localhost:8080/gadgets/ifr?url=http://www.labpixies.com/campaigns/todo/todo.xml&view=home

After this point you have a minimal requirement to use gadget renderer inside your web-app, have fun.