The question just came up at work, do you use one “l” or two when you spell the past tense of cancel (canceled or cancelled)? It turns out both are valid, but which one is preferred?
Maeve Maddox at DailyWritingTips says:
The double l in cancelled is British usage; the single l is American usage... In American usage, the final l is doubled only when the stress falls on a syllable other than the first. Where British usage calls for levelled, libelled, quarrelled, and travelled, American usage has leveled, libeled, quarreled, and traveled. American usage agrees with British on annulled, controlled, patrolled, and extolled because the stress falls on the second syllable of these words.