Look at
www.homebrewing.org for used kegs. Cheap shipping, and they guarantee them or they'll pay return shipping. Check the "loose handle/bottom" kegs. I have 6 from them, and only had to add a dab of Gorilla Glue to 2 of them to make them like new. A little soak in oxyclean and they're good to go. Great value for the price, and they are honestly very good kegs! IMO, the quality of new kegs are not as good as the old/used ones. Especially these new, cheap China kegs. Poor stainless grade.
Check
www.ritebrew.com for parts. Their taps/shanks and manifolds are some of the best prices on the internet, and again cheap shipping.
www.bargainfittings.com for stainless fittings. You absolutely cannot beat his prices. Well, unless you want to scour McMasterCarr for 3 hours to to end up saving $2...
Check your local Craigslist constantly. You should have no problem finding a used co2 tank and other necessities, if you look daily.
Check the "For Sale" section here too! Great deals pop up all the time, but you gotta be quick. There's also a guy in that section with great prices on shipped co2 tanks too.
Many people like the "big" websites, but generally I find them laughably overpriced. You can find great deals if you take your time and search everything. Sometimes you'll find great stuff on eBay and Amazon too!
Make sure you put a fan in your keezer to circulate the air, and make sure the freezer is airtight. 2 big mistakes I made when I first built a keezer.
A good rule of thumb is 1ft of 3/16 beverage line for every 1lb of co2. Then cut the lines back until you find your perfect pour. Most of my ales run at 12lbs with 9 3/4ft lines at around 36°. Remember, everyone's system is different... and yours will be too! I coil my lines up, zip tie them, and lay them on the top of the kegs.
Buy Perlick taps. You will not be disappointed. Don't waste your money on standard taps. Even the chrome/brass Perlick taps are infinitely better than the standard ones. They are worth their weight in gold...
Good luck, and happy hunting!!!