For DIY, here's a basic parts list:
For each keg:
Dispensing: 1 liquid disconnect (barbed = cheaper), hose clamp, 6' hose to fit barb, picnic tap.
Gas in: 1 gas disconnect (barbed), 2 hose clamps, ~3' gas hose.
Also need:
4-way gas manifold with barbed (gas hose size) shutoff + check valves (4 valves total).
gas hose from regulator to manifold (3' should be ok), 2 hose clams for this hose, fitting to connect to regulator.
Regulator: minimum = 1 gauge (recommend: 2 gauge) regulator.
CO2 tank.
Personally, I have a 3 gauge regulator (two outputs at different pressures) and I use disconnects with threaded fittings. These are optional upgrades, what I quoted you is probably the cheapest you'll get.
I just priced out everything from Midwest Supplies, and it came to $253.15. Their quadruple tap draft system with kegs is $279.95. Granted, you could save a bit of money by shopping around for the best price. Getting the CO2 tank and regulator from Micromatic instead will save you about $30.00 depending on shipping. Get what you can at your local hardware store to save even more (the manifold, hose clamps, and barbed disconnects).
Hope this helps.