Air carrier Captain laments the delays and wasted fuel on a clear day at ORD at peak arrival time.

Narrative

Prolonged vector at slow speed; ATC saturation; low landing fuel. We received an inordinate number of speed changes and odd; unusual vectors getting to ORD; and once in TRACON's hands; we expected that we would be sequenced efficiently. Instead; a B757 and an RJ were stuck in front of us; and we were held back at 170 KTS from the eastbound turn off the arrival until SIBLY on the inbound approach. The vectoring took us well outside Class B airspace; and we used an additional 1400 LBS of fuel getting from roughly the airspace over Rolling Meadows up to the airspace over south Park Ridge. I'm putting in this report not because of anything special but because it is so easy for our minimum fuel that dispatch provides us to get burned up by C90 TRACON and ZAU Center. We blocked in with 4300 LBS - much lower than the FAT of 6000 LBS expected. There were no other delays and we were ahead on fuel number over Mason City VORTAC (MCW). From that point on; Center began using the 'speed up; slow down; vector off course' technique of separating aircraft. There was no weather to speak of; just a cloud layer over ORD. All three west landing runways were in use; and it was peak arrival time.