Migration from Joomla
I've used Feeds and Menu Export/Import to migrate Joomla sites to Drupal a few times. It's a little tedious but it works.

I think the next time I have to migrate  Joomla site to Drupal I will use the Joomla to Drupal module. It doesn't appear to be regularly updated but looks like it should work for Joomla 1.5 and less. I don't think it will be useful for Joomla 2.x and up though.