If you’re stuck with a custom launcher (e.g. OUYA’s) and want to get back to the stock launcher, first connect with adb:

adb connect 192.168.56.101
adb shell

Then, in the shell, punch in the following

am start -c android.intent.category.HOME -a android.intent.action.MAIN

This will dispatch an intent filtered by category android.intent.category.HOME and action android.intent.action.MAIN. You should also be able to dispatch an explicit intent, passing the full package and class name:

am start -n com.android.launcher/com.android.launcher.Launcher

Sadly, this didn’t work on AndroVM’s 4.1.x; perhaps the launcher’s name is different. Not that I care particularly 😉