WordNet (r) 3.0 (2006):

drag on
    v 1: last unnecessarily long [syn: drag on, drag out]
    2: proceed for an extended period of time; "The speech dragged
       on for two hours" [syn: drag, drag on, drag out]

Moby Thesaurus II by Grady Ward, 1.0:

47 Moby Thesaurus words for "drag on":
   abide, be infinitely repetitive, be tedious, bide, carry on,
   cease not, continue, continue the same, crawl, creep, drag,
   drag along, drone, endure, fatigue, glut, go along, go on,
   go on forever, hold on, hold steady, hum, irk, jade, jog on,
   keep going, keep on, linger, linger on, never cease, pall, persist,
   prevail, remain, run on, run through, satiate, slog on, stagger on,
   stay, stay on, tarry, tire, tire to death, wear, wear on, weary