The information below has been updated to reflect changes to Docker Hub.
At cloud.docker.com/u/[docker_ID]/repository/list you can see and manage your various repositories.
Clikck on a repository to make change to it. You can mark it as public/private, provide a description, link to GitHub or BitBucket for Automated Builds, add collaborators and webhooks, and more.
Delete your repository from under the 'Settings' tab.
Note: if you delete a repository, all images within it will be permanently deleted as well!