Our current http://drupal.org/cases section is very sad. We should make it show off how awesome Drupal can be with pictures, how-tos, case studies, and more!
Drupal.org is a bit painful to browse on a mobile device. It'd be cool if it used responsive design to show off what Drupal can do!
Move job postings out of groups.drupal.org and onto drupal.org, and improve the listings with ties back to companies and locations + featured listings to help fund d.o development.
Show upcoming events in your area, show what events people are going to on their profile, show a map of events around the world, etc.
The current Drupal Services listing at http://drupal.org/drupal-services is just a bulleted list of companies in alphabetical order. A better listing could allow people to search by country, business sector, and could also prominently feature companies that give back to the project.