If you ordered an X-Server without a video card, but need one here’s a down-n-dirty tip:
If you have an old B&W PowerMac lying around, swipe the video card from it and use it in the upper slot. It works fine, won’t void your warranty and gives you the basic functionality you need to manage the beastie!
Ed. Note: I think most Apple PCI video cards, note not AGP, should work in the Xserve, but nice to know of a specific example. Having said that….running it headless isn’t hard to do, either.