The ability to hook a gaming system up to a computer monitor depends entirely on the system, as well as the monitor. If you are willing, sign up for the forums and let us know what type of monitor you have (Brand and model number, if possible) as well as what gaming system(s) you are planning on hooking up to said monitor. With that information, we'll be able to guide you in the right direction 
Thanks for you question!
JB
As Juice said, it really depends on the system you're trying to connect with, what cables for that system that you're using, and what connectors the monitor has on it.
I'll try to summarize the most common combinations here.
If your monitor has HDMI and you're trying to connect an XBox 360 or PS3, you can use an HDMI cable.
If your monitor has DVI and you're trying to connect an XBox 360 or a PS3, you can use an HDMI to DVI converter. There are both full cables and small adapters for this.
If you monitor only has VGA(or D-SUB), then you would have to buy a converter for whichever connector you're using on your console to convert it to VGA. In some cases these don't exist, but they do in most. Some of these converters are fairly expensive as well. Futureshop does not currently carry these that I'm aware of.
The last option is you can use a TV Tuner with your PC to connect the console to your PC, which will send the video to the monitor.
If you're using an XBox 360 and only have a VGA connection on your monitor, you can use the XBox 360 VGA Cables as shown here. I use these at home; the picture quality is great.
Thats what I use as well Tanarus , then I use RCA Barrel Connectors on the end of the Xbox's 360's VGA adapter (the RCA cables Red/White) and then plug a Rca to Mini adapter into that and then plug the mini into my computers line in for my sound. Personally I use headphones but any pair of computer speakers will work as well
