You will need-
Keg(s)
CO2 regulator
gas and liquid lines
means to chill the keg
serving faucet
I am in the middle of building a side by side kezzer/ferm chamber, but I am still using picnic taps for the time being.
Depends on how big of a hurry you are, I spent a year picking up a piece here and there when I found good deals. Craigslist is a good place, as well as the FS thread here on the forum, you have to keep an eye out because deals go quick.
You could always look into buying a package, looking at kegconnection.com you can get the basics of what you need for a 2 keg setup for ~$265 + shipping ( for pin lock kegs)