It seems that, from Google Cloud Console there is no way to delete a project.
Note: As of 2013-09-19 this is no longer an issue because Google had fixed
Step By Step to disable and request permanent deletion from Google Cloud Console and Google Appengine Project.
Step 1 - Navigate to appengine project and Click on Application Settings.
Step 2 - Scroll/Find the button to Disable Application. Click the button.
Step 3 - Click on "Disable Application Now"
Step 4 - Click on "Request Permanent Deletion". You will screen update showing the scheduled delete.
Step 5 - Navigate to Google Cloud Console. The status corresponding to the disabled/deleted project is shown as "Disabled" in red.