A couple of questions:
1) What's your budget?
2) How much do you brew/drink?
If you're trying to do this cheaply, look on craigslist for a cheap/free fridge or freezer. If not, well, you can spend a lot of money. Kegging, like most homebrewing, can get expensive. If you have a spare fridge, I'd start with that. Depending on the size of it, you can fit anywhere from 2-4 corny kegs in one.
Depending on how much you drink or like variety in your homebrews, I'd suggest more is better. I have a mini-fridge that I converted into a 2 keg kegerator and I wish I had at least 4 taps on hand.
The first thing you'll want to decide is ball lock (Pepsi) vs. pin lock (Coke) corny kegs. Ball lock are more common than pin lock but you can still get parts for either one without an issue from online vendors. The more important thing is that ball lock kegs are taller and narrower while pin lock are shorter and wider. You'll want to figure out which is best for your kegerator in terms of fitting the available space. Also realize that you'll need at least ~6" above each keg for the disconnects.
You'll also need a regulator, gas and liquid disconnects, beer (inner diameter 3/16") and gas (ID 1/4" or 5/16") lines, picnic (aka Cobra) taps, hose clamps, and a CO2 tank at the minimum. You do not need to store the CO2 tank in the fridge, contrary to what a lot of people do. You will need at least 10 feet of beer line.
Like I mentioned before, if you diligently check craigslist, you can get a lot of this stuff for next to nothing. If you don't care to do that kind of leg work, I'm sure one of the kits from kegconnection or kegcowboy would be great.
