Luckiest. Intern. Ever. Seriously! Can you imagine having this on your resume as an internship? Outstanding opportunity.
When I first started using Eloqua, I pulled a LOT of reports. We were doing a data cleansing project and I pulled reports to help figure out our highest priorities. Then once we started, I pulled reports to help keep track of the progress. It taught me to a) pull reports and b) analyze and interpret the data so I could present it to my team in a condensed fashion.
Love Kristin Connell's idea of standardizing foldering structures and naming conventions. Not the sexiest of projects, but very helpful for the team and valuable experience for your intern if they go on to use Eloqua later in their career.
Also, consider enlisting their their help with manual tasks. In a perfect world, everything would be automated (*swoon*), but we all have manual tasks. Having someone who isn't part of the day-to-day handle these items for awhile could prove useful. It takes some work off you, and they may come up with a solution you haven't thought of to make the process better/easier.
Good luck!