Yes, most cruises have 1 formal night. If you go here
, they will tell you how many formal nights there are on a cruise of a given length.
2007 - Majesty of the Seas (Bahamas)
2009 - Enchantment of the Seas (Western Caribbean)
2010 - Freedom of the Seas (Western Caribbean)
2013 - Golden Princess (Alaska, roundtrip from Seattle)