Disney cruises are departing all year round. You can set sail on cruises during the week, those that depart over the weekend. There are many cruises of different lengths available, depending on how much time you have to travel. You can take a quick long-weekend 3-night/4-day getaway around the Bahamas, or depart on a longer 15-night cruise to the British Isles or Norwegian Fiords.
Disney offers a greater number of cruises during spring break, when many people find time to travel. But you can also cruise during the offseason, when you may have less people to deal with and find better deals. My favorite site to visit to look at Disney cruises at a discount is Cruise Direct. You may choose to cruise in November when it might be less busy; it may book up faster over holidays when most people have off from school and work, whereas as a cruise in January, after Christmas, would be one of the less expensive months, as everyone is back from holiday.
Holiday cruises are designated as “Very Merrytime Cruises”, similar to Mickey’s Very Merry Christmas Party in Walt Disney World. If you happen to travel with Disney Cruise Line during the holidays, on this Merrytime Christmas cruise you will enjoy all the Disney magic, plus the added magic of Disney during the holidays!
A Walt Disney World  Resort can be a great place to stay before your cruise leaves, or after you get back, if you want to extend your vacation.