It depends on how old and what model of Mac monitor you're talking about. As long as it's not old and doesn't have an ADC connector you'll be fine. I'm currently running an Apple 23" Cinema Display on my linux machine - just hooked up via DVI like any other recent monitor. I would kind of recommend against buying a Mac monitor, though, as they tend to lack functionality. You likely won't have any configurable options or OSD on the monitor and most likely it will only have a single input. It will also be much more expensive than what you can get elsewhere with the same performance/capability.