Priceline.com & Expedia: Select Roundtrip Flights (New York, Chicago, Los Angeles & More to Singapore) from $328

From Priceline.com:
* Departs ORD, Chicago via Priceline from $328 Round-trip Flight

August: 28
September: 4, 11, 18, or 25th
October: 2, 9, 16, 23, or 30th
November: 6, 13, or 27th
* Departs LAX, Los Angeles via Priceline from $325 Round-trip Flight

April: 26th
August: 28th
October: 2, 9, 16, 23, or 30th
November: 6th
* Departs DFW, Texas via Priceline from $417 Round-trip Flight

August: 28th
September: 18, or 25th
October: 2, 9, 16, 23, or 30th
November: 6, 13, or 27th
* Departs SFO, San Francisco via Priceline from $433 Round-trip Flight

April: 21, 22, or 23th
August: 28th
September: 18th
October: 2, 9, 16, 23, 26, or 30th
November: 6, 13, or 20th

Expedia :
* Departs JFK, New York via Expedia from $327 Round-trip Flight

September: 12, 18, 19, or 25th
October: 2, 3, 10, 16, 17, 23, 24, 30, or 31th
November: 6, 7, 13, 14, 27, or 28th
* Departs BOS, Boston via Expedia from $416 Round-trip Flight
October: 17, 18, 19, or 24th
November: 1, 7, 8, 14, 15, 21, 22, or 29th
December: 5th
* Departs SAN, San Diego via Priceline for Expedia from $440 Round-trip Flight

October: 16, 23, or 30th
November: 6, 13, or 20th