This is a big one. Microsoft is now supporting Drupal (and Wordpress, no Joomla it seems). They offer PHP web app downloads to promote the fact that Windows Server now ships with PHP support, certified by Microsoft and Zend. Drupal is at the top of the lists. This is big.
I manage the Los Angeles Drupal user group and each year we throw a free DrupalCamp in or near Los Angeles. One of our key sponsors this year is Microsoft and they were great about it and ended saying a lot at the camp about their support for PHP & Drupal.
NOTE: The Drupal download is actually Acquia Drupal, a free extended version of Drupal by a commercial company that was started by the founder of Drupal.