Don't get me wrong, I've had my setup for over a year, and it still amazes me.  When I think back 10 years to when I first saw a Guiness pour and was amazed by the cascading and the thick head, I never thought I would be able to have that in my own home.  Now when I have an Irish stout on tap, it rarely lasts more than a week (and that's when only I drink it).

You can fill the kegs with homebrew, or you can fill kegs at your local pub.  Most breweries will be happy to fill kegs for you - especially if they are clean and sanitized.

I like to differentiate a kegerator from a beer fridge because I usually think of these pre-fab True Brand things when I hear the word kegerator.

A beer fridge would be some kind of homemade system.  Kegerators are available for about $1200 for a single tap like in the picture.  I made mine for about $150.  Although I stole a couple parts from work and I picked up the fridge for $20.

So you will need:

A refrigerator (of course).  A studio apartment sized fridge works well.

Taps (sanke, cornelious, etc.)

Faucet wrench

CO2 cylinder

CO2 regulator

Hose (8-10 feet per tap, 5/16")

Faucets (1 for each according tap/keg) (stainless works great, and doesn't tarnish like brass)

Assembled Nipple Shanks (1/4" ID, 3" long)

A manifold or cross to split the CO2 line off the regulator

Drip Tray

Pint glasses and an appetite for beer.

You first have to decide how many taps you are going to have.  My fridge isn't that large, but can hold (3) 5 gallon kegs, or (1) 15.5 gallon keg.  I drilled 3 taps to account for the former.  I like to have a variety, so it's appropriate.  If you're only going to buy 1/2 barrels from the store, maybe only drill one faucet.

The shanks are 1" in diameter.  But you should use a 7/8" hole saw to drill the holes.  This makes sure there isn't any extra space for cold air to escape.  You will probably have to end up screwing the shanks into the fridge.  It will be tight - but that's a good thing.  Put the shanks through and secure them with the retaining nut on the back side.  Be careful because it's only plastic on the inside, but make them tight enough so the faucets don't spin around on the front.

If your refrigerator has a freezer, make sure you don't drill the faucets too high so the freezer door opens the faucet (like I did).  Drill them low enough for the door, but high enough to not  have to bend down too far.  If you have a top loading freezer, you will need a tap tower that will be drilled into the lid. 

You can also put the CO2 cylinder in the refrigerator with the kegs if you have room.  It works just fine at colder temperatures.  I don't have room, so mine sits on top of my fridge,  and the gas line goes through a small hole drilled in the side of the fridge.  I don't have a manifold or secondary regulator bank, so I just have a cross that splits the one gas line into 3 lines.  The problem with this is that when a new keg goes on tap, and its pressure is higher than the other kegs hooked up to the system, it will push the blow off from the higher pressure keg into the gas lines and into the other kegs.  You can avoid this by simply not connecting the gas line until the pressure has dropped by pouring a pint or two.  You can also see that I have a spot in my apartment that was made for a beer fridge.

Next cut some hose to connect the kegs to the shanks in the door.  You will need about 4 or 5 feet of hose to properly dispense the beer.  I've seen setups in homebrew shops that have a faucet directly connected to the "out" line of a corny keg.  There will be too much pressure coming from the keg when the beer hits the tap, so you will get a lot of foam.  With about 4 feet of hose, you can dispense at 8-10 lbs, which is enough to push the beer without foaming, and it's not enough to saturate the beer.  It also allows you to open the door and have enough hose to keep from pulling the kegs out.

Next attach the drip tray under the faucets.  Allow enough room to fit a pint glass, or an imperial pint glass underneath it.  Some drip trays have drains, but sometimes it's hard to make the beer drain somewhere.  If you have a drain close by in the floor, run a hose from the bottom of the drip tray to the drain.  Be careful because the sweet beer may attract fruit flies.  If there is no drain, just be careful and empty it often.

If you want to have a nitrogen faucet, you have to do a little more work.  You can get a 5lb. nitrogen cylinder (they actually measure it in cubic feet), and a nitrogen regulator ($45 from Rapids), and a stout faucet($74 from morebeer.com).  Even wholesale, this costs about $200, so it's not very feasible.  I have tried pushing a nitrogenated beer through a stout faucet with CO2.  This works for a couple days, then the beer gets over saturated with CO2.  You also need to bump up the pressure to at least 15lbs (preferably more to get the proper cascading effect), so without a proper manifold or ganged regulators, your other beers will also get over-carbonated.  But it is absolutely worth it if you can make it work.  Just keep a very close eye on all your beers and it will work.

You can use either blended gas ("Guiness Gas" 75%N2, 25%CO2), pure nitrogen, or use a blender.  The blender will allow you to hook up two cylinders of gas and adjust the blend.  Guiness gas is good for 'carbonating' and achieving the perfect blend of gas dissolved in the beer.  Pure nitrogen works just fine for pushing the beer, and for nitrogenating, but you would also need to add CO2 yourself, or use the natural carbonation of a beer in a keg.

The beer line cleaners you can get at a homebrew shop are OK.  "BLC" (beer line cleaner) is a caustic cleaner (sodium hydroxide), which is the best thing to clean your lines with.  Caustic kills any bacteria or mold that might have gotten into your lines.  It also hydrolizes hops and proteins in the lines.  They might want to sell you a hand pump to push the chemicals through, but you can mix it in a corny keg and push it through with CO2.  Don't shake the keg though, because CO2 and caustic don't react very well.  But at 10 lbs of pressure, you won't have a problem.  Hot water works best.  Make sure you rinse thoroughly after cleaning.  You don't want to drink caustic (trust me on that one).  Also make sure you don't get any on you.  Wash your hands soon after handling it.  I've had it burn through a pair of shoes, and also 'burn' my legs when it splashed on me.  It's powerful stuff, so respect it.

I also like to keep a spray bottle of sanitizer near by for when I switch kegs and for when I won't be using the faucets for a while.  I give the faucets a few sprays to keep bacteria from growing inside and dirtying the lines and spoiling the beer.

Assembling the pieces is the easy part.  Knowing what you need is the hard part.  Some parts will be trial and error, which for the most part is no big deal.  When you are drilling holes into metal, then it sucks (as I found out). 

You might also end up needing some kind of fastener to hold the door close on the refrigerator if it is a small one.  The hoses and kegs seem to push the door out if it doesn't seal well.  A latch like on a toolbox would work well to keep the door shut.

You can get a lot of the pieces from a good homebrew shop like Beer, Beer, and More Beer.   You can also order from Rapids or Foxx (I prefer Rapids), but you are supposed to be a brewery or homebrew shop.  I'm sure your local shop will be happy to order all the parts for you, but possibly at a marked up price.  You can try calling Rapids, telling them you are a homebrew shop, give your home address and your credit card number, and hope it works.  I think it will. 

Most of all, enjoy the beer, and have parties to move the beer through the lines and to show off.  Why not?