The best person to answer this question is you - as you're the one with all the required information at hand - we can't keep track of all the models of Macs and computers out there of course.
The basic approach is to very simply check the manual/specifications for your machine to determine what monitor outputs you have (and you can read more about monitor connectors here). All our monitor pages have a specifications page listing the monitor inputs.
In short, for PCs: almost any modern PC(say built within the last 5 years) will easily handle a 26" or smaller monitor, using a DVI output and almost all monitors come with a DVI cable now.
In short, for Macs: With newer Macs, most of the time you will need a display port or mini display port to DVI adaptor available from any Mac store. A lot of older Macs have DVI outputs on them, in which case you're in the same boat as PCs above. Just check your Mac and our article about connectors and you should find it very easy to work out. Any Mac from at least the last five years will be fine with 26" and smaller monitors.
If you're buying a 27" monitor or bigger - you will need to check your video output can handle the high resolution of these monitors. This will be listed in the specs for your machine/video card. These monitors usually connect with a Dual Link DVI cable or via DisplayPort.