Benchmarking an entire IS/IT Department

ferretworks writes: "Our IS/IT department has been asked by our CEO to find a way to benchmark ourselves against IS/IT departments from other companies with similar technologies (none specific). This sounds like an innocent enough request, but diving into it has made me realize that this is, not necessarily undiscovered country, but a desolate one and rarely visited. So, my poll to the Slashdot community is: In your Opinion, what is best way to benchmark an IS/IT department and what categories/sub categories would you base your judgment and ratings on for a proper benchmark."