Campaigns/traffic sources/creatives can't be deleted, but they can be Archived. Clicking the status column (typically Online or Offline) next to campaigns/traffic sources/creatives, will reveal a drop-down menu allowing you to select Archived. Once chosen, your campaigns/traffic sources/creatives will be set to "Offline" and will also disappear from your dashboard.
You can view your archived campaigns at any time by selecting All from the search toolbar.
