I will discuss the ongoing work on ULIRGs found by the Spitzer surveys (xFLS, GOODS, FIDEL, COSMOS). Most of the research to date has concentrated on the Spitzer-24um band given its high sensitivity, but the extrapolation from the observed mid-IR band to the total infrared luminosity is highly uncertain. Recent deep 70um and 160um observations have been used to constrain the total infrared luminosities of the 24um-selected populations and to identify the brightest far-infrared sources in the fields. Initial CO follow-up observations will be presented and future possibilities for Herschel will be discussed.