Mattias Skarin recently posted a useful 2-page summary of his approach for managing a support organization using agile techniques and a kanban board.
I recently led a team of Solutions Consultants (who supported our customers development efforts) at IP Commerce. The challenge we had was that there was ALWAYS a full backlog of customer support tasks, and those tasks are virtually always a higher priority than project-based work that the team needs to get done - stuff like improving the process, creating sample applications, writing documentation.
What I did to solve this dilemma was to allocate 20% of each person's time for project work, with 80% for ongoing customer support. The team members scheduled their time to carve out 4 or 8 hour time blocks during the 2-week iteration where they could focus on project work.
For iteration planning purposes, I kept a backlog of project-based user stories only - no customer support tasks - and the team planned how much of that backlog they could knock out in 20% of their time. The customer support stories/tasks weren't considered during planning - we knew those would flow in steadily.
This worked well for us, but let me know if you have other advice on managing support organizations.