What does it mean "No Launcher activity found!"

Here's an example from AndroidManifest.xml. You need to specify the MAIN and LAUNCHER in the intent filter for the activity you want to start on launch

<application android:label="@string/app_name" android:icon="@drawable/icon">
    <activity android:name="ExampleActivity"
              android:label="@string/app_name">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

Multiple action tags in a single intent-filter tag will also cause the same error.

Like Gusdor said above, "Multiple action tags in a single intent-filter tag will also cause the same error." (Give him the credit! I could just kiss Gusdor for this!)
I didn't find any docs for this fact! I had added a new (USB) action and being clever, I lumped it in the same intent-filter. And it broke the launch. Like Gusdor said, one intent filter, one action! Apparently each action should go in its own intent filter.
It should look like this...

<intent-filter>
  <action android:name="android.intent.action.MAIN" />
  <category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
<intent-filter>
  <action android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" />
</intent-filter>

When I did this, WAZOO! it worked!

Do you have an activity set up the be the launched activity when the application starts?

This is done in your Manifest.xml file, something like:

    <activity android:name=".Main" android:label="@string/app_name"
        android:screenOrientation="portrait">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>