We are currently in the process of trying out FogBugz on a SCRUM based project.
We are still very much finding our feet with SCRUM (and FogBugz) so what we are doing may not be 'pure' SCRUM.
First of all, we are using Excel for the release backlog e.g. what we will be delivering in version x.xx
I had actually written a blog post on using FogBugz as a backlog but ended up going with Excel as what I was proposing was a bit complicated in retrospect and I don't think I was really gaining anything.
In the backlog spreadsheet we keep the name of the back log item, a size estimates, so we can calculate velocity, and some other information such as which sprint we will deliver each item in.
We keep our product specifications in the FogBugz wiki and add links to this from each entry in the backlog.
In Fogbugz we map releases to sprints and use schedule items to track our tasks for each backlog item.
Before we start a sprint we choose which backlog items we are going to deliver in this sprint. In FogBugz I create a new release and set the end date to two weeks down the line. We then break down the chosen backlog items in to tasks and add them to the release as 'schedule items'.
Everyone estimates their own tasks and tracks time against them using the 'working on' menu as you normally would. Every day the team members revise their estimates and we can then use the various reports to see how things are progressing. The ship date confidence chart give you a sort of reverse burndown.
Each member of the team also has a 'status' schedule item that they edit every day to record there status report for the daily stand up meeting e.g. what did I do yesterday? , What am I doing today? What obstacles are in my way?
As you can see we a really just using FogBugz for task management.
We picked it more for the EBS and the Wiki.
So far it's working quite well but the project I'm using it one is a 3 person 6 week project.
Hope some of this helps. Let me know if you need any clarification.
Edit: I'm also not trying to get the perfect system up and running first time. I'm very much taking the approach of trying something out and if it's not working out, then change it. So far so good with FogBugz though.