Drupal is one of the leading open source content management systems - some would say the leading open source CMS. We've had a few requests over the years for OpenSSO/Drupal integration, but no one has hitherto stepped forward. Finding myself with a few spare hours over the last few days, I decided to investigate.
It turns out that, thanks to Drupal's extensibility through modules and OpenSSO's identity services, it's pretty straightforward to get something working. So I did. There is now an OpenSSO module for Drupal [ README | Source - also available via Subversion]. I'm no expert in either PHP or Drupal, so there may well be bugs, but it seems to work well, checking for the OpenSSO cookie when users attempt to access Drupal, redirecting them to OpenSSO to authenticate if necessary, and retrieving a Drupal username from the user's OpenSSO profile before setting up the user's Drupal session.