Xamarin.Android での Google Map(というか Play Service) 利用が、本家より簡単になった件 ref: http://qiita.com/amay077/items/14191c808e9cac4eae2c

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
    android:versionCode="1" 
    android:versionName="1.0" 
    package="com.amay077.sample.googlemapv2sample">  <--------※1


    <uses-feature android:glEsVersion="0x00020000" android:required="true" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />


    <uses-permission 
        android:name="com.amay077.sample.playservicesample.permission.MAPS_RECEIVE" />   <--------※1
    <permission 
        android:name="com.amay077.sample.playservicesample.permission.MAPS_RECEIVE"   <--------※1
        android:protectionLevel="signature" />

    <application android:label="GoogleMapV2Sample">
        <meta-data 
            android:name="com.google.android.maps.v2.API_KEY" 
            android:value="AIzaByD1jiFER3le_HFrkOrEhaNIsemoNoDesuU" />  <--------※2
    </application>
</manifest>

Main.axml

<?xml version="1.0" encoding="utf-8"?>
<fragment xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/map"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    class="com.google.android.gms.maps.MapFragment" />

MainActivity.cs

using Android.App;
using Android.OS;

namespace GoogleMapV2Sample
{
    [Activity (Label = "GoogleMapV2Sample", MainLauncher = true)]
    public class MainActivity : Activity
    {
        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);

            // Set our view from the "main" layout resource
            SetContentView(Resource.Layout.Main);
        }
    }
}