Kits, in my opinion, aren't really much easier than setting up a system piece by piece. By putting a system together yourself you can ususally save a little cash too.
You will need a water block for the cpu. Danger Den, Gemini Cooling, and Swiftech all make good blocks and are competetive in price.
A radiator of some type: heater core from a car, tranny or oil cooler or one of the ones offered by the places mentioned for the wb. I prefer heater cores due to price and effeciency. The other method would to be building a bong. Look under tips and techniques for info on bongs.
You will need silicone or vinyl hose, silicone is better but slightly more expensive. Ten to fifteen feet is enough and should give you extra incase you make a bad cut etc.
You will need a fan or two to cool your rad. Most people use two 120mm fans depending on rad size in a push pull config.
Hose clamps are not always necessary but are good insurance though I only use one in my whole system.
A good pump: Eheim 1048 or 1250, Cap, Rio but definitely not a cheapy from Wally World aka Walmart. You shouldn't try to cut corners on this at all imo.
Links:
http://www.dangerden.com
http://www.geminicool.com
http://www.case-mod.com
Any other questions fire away!
Also before you setup a watercooling system always run it outside your case for 24 hours to make sure there are no leaks!
