These are, or at least seem to be, the harder to find intents or the ones I use most commonly. There are also published ones at https://developer.android.com/guide/components/intents-common
Google Navigation
Launch Google's Navigation By Location - Driving
new Intent(Intent.ACTION_VIEW, Uri.parse("google.navigation:ll=" + mLatitude + "," + mLongitude));
Launch Google's Navigation By Location - Walking
new Intent(Intent.ACTION_VIEW, Uri.parse("google.navigation:ll=" + mLatitude + "," + mLongitude + "&mode=w"));
Launch Google's Navigation By Address - Driving
new Intent(Intent.ACTION_VIEW, Uri.parse("google.navigation:q=an+address+city"));
Google Map with Pin
new Intent(android.content.Intent.ACTION_VIEW, Uri.parse("geo:0,0?q=51.123456,-114.123456 (" + pinName + ")");
Google/HTC Calendar
Launch Google's Calendar - non-standard
Intent calendarIntent = new Intent();
calendarIntent.setClassName("com.android.calendar", "com.android.calendar.AgendaActivity");
or
Intent calendarIntent = new Intent();
calendarIntent.setClassName("com.google.android.calendar", "com.android.calendar.LaunchActivity");
Launch HTC's Calendar
Intent calendarIntent = new Intent(Intent.ACTION_MAIN);
calendarIntent.setComponent(new ComponentName("com.htc.calendar", "com.htc.calendar.MonthActivity"));
Use the package manager to determine which one is active on the device.
final PackageManager packageManager = getPackageManager();
List<ResolveInfo> list = packageManager.queryIntentActivities(calendarIntent, 0);
if ( list.isEmpty()) { ....