Excel is one of the most popular tools for managing the backlogs of the Scrum process. There is a number of templates available and here is a screencast on using one of the advanced ones. This template was created by Petri Heiramo from Digia and includes facilities for managing both product and sprint backlogs. You can download this template on the page with the collection of Scrum templates and examples.
You might also like to have a look at the video tutorials on the simple product backlog template and simple sprint backlog template.
