While we haven’t decided yet exactly which CMS platforms will be included in the competition, you should definitely expect to see Drupal represented, as well as other products like Joomla!, Expression Engine, and WordPress. The final selection will be made at the same time that we pick the benefiting organization, and will be based on their needs and capabilities.
Even though SXSW isn’t until next March, we have some pretty big plans for this session, and we’ll be posting more details here as they become available, so stay tuned!

SXSW Showdown Comes North, by Northwestern ;)
George, This is a great!
We've got many fans in Chicago and Evanston, highly anticipating the spread of carnage from your Showdown at South by Southwest.
We're fortunate that Palantir.net is hosting Chicago Shootout, a re-match on April 29th in Evanston, Illinois, home to Northwestern University (hence "North by Northwestern" note - assuming all participants are wearing bullet-proof vests at SXSW. :)
Oh, plus, George has added Alfresco into the mix. Ahhh, fresh blood ;)
It's all in good fun (and business) as folks from all walks of in the OS CMS world will get a great look under the hood of these fantastic CMS solutions - close-up!
Drupal - Joomla! - WordPress - Alfresco
http://CMSX.us