An A320 Flight Crew departed on a transcontinental flight already concerned about their planned arrival fuel. Weather; traffic congestion and an ATC directed go around at their destination due to traffic on their runway precipitated an Emergency Fuel declaration and expedited arrival handling.

Narrative

Prior to departure; we called Dispatch to discuss the weather and planned fuel upon arrival at our destination; in particular the tornado watch in the northeast. Dispatch advised us the weather shouldn't be a factor but we have an alternate due to a low ceiling and we can't pick up additional fuel because we were at our maximum takeoff weight. We were dispatched with 40;100 LBS of fuel. Departure; climb; cruise and initial descent were normal.During the initial descent we received holding instructions and an EFC (Expect Further Clearence) of XA45Z. We sent an ACARS to Dispatch with the holding information and an FOB of 10;000 LBS. We briefed the need to exit the hold and proceed to our alternate by time XA57Z or 6;700 LBS fuel remaining. Destination ATIS indicated: wind 190/17G24; vis 9 SM; SCT 007; BKN 031; BKN 140; BKN 250; 22/20; altimeter 29.71. ATIS at our alternate indicated: wind 220/12G17; vis 10 SM; SKC; 25/14; altimeter 29.65.A short time later we were cleared to leave the hold and continue our STAR and we sent an ACARS to Dispatch advising them. During the descent and arrival the instrument approach was changed three times; from the left runway to the right and then back again to the left. ATC vectored for the approach behind a heavy foreign carrier ahead of us on the approach. We contacted Tower when established on the approach and were cleared to land. Passing 1;000 FT on the approach we heard the Tower multiple times giving taxi instruction for the foreign carrier to exit the active runway. Each time the carrier replied inaccurately. At 500 FT the Tower instructed us to Go-Around due to traffic conflict on the runway. ATC vectored us around for another ILS approach. We were positioned behind several arrivals on downwind at 4;000 FT where we advised the passengers about the Go-Around; the conflicting traffic on the runway and advised them we should be landing shortly.Reviewing the fuel situation on the downwind leg the fuel was around 5;700 LBS; we briefed the need to declare Minimum Fuel if ATC delayed our vectors. We were still on downwind behind several arrivals with no sign of vectors towards final approach. We declared Minimum Fuel with around 5;200 LBS fuel remaining and briefed the need to declare Emergency Fuel if ATC further delayed our vectors. After we called ATC to expedite our approach without any resolve we declared Emergency Fuel with around 4;500 LBS fuel remaining. Immediately ATC started vectoring us towards the final approach; handed us over to Tower; cleared us for an approach and cleared us to land. The approach and landing were normal. Upon touchdown we had around 3;700 LBS fuel remaining and taxied to the gate on aircraft own power with no further assistance needed.