When is the least busy time of year for Disney World? When should I go there such that there are the least number of people there?
We went to Disney this March (beginning of the month) and it was almost empty (5 minute lines for almost every attraction). This was before the school break.
I followed this link that gave me the dates to avoid (see the site for reasons):
The best time, generally, is when kids are still in school. This won't guarantee a less crowded park, but it helps. This means late Jan/early Feb, as long as you dont go around Presidents Day, late April/early May, late Sept through early November (though this is also Epcot Wine and Food festival time leading to larger crowds in EPCOT), and early December.
Early December is my favorite, because the parks are all decorated for Christmas, the weather is cooler, there are fewer rides down for maintenance (which usually happens in January-March), and it is usually value season with regards to hotel rates. And the crowds are usually pretty light, because parents are less likely to pull their kids out of school with one to two weeks left before finals.
The one thing to watch with early December is when the Pop Warner Football / Cheerleading championships are. I didnt find that it added to the crowds any, but some people find the large groups of pre-teenagers annoying. I still feel like this isnt enough to knock early December from my top spot, as the other times of the year have their own pitfalls as well (Jan/Feb = maintenance time for lots of rides, May = hot, Sept/Oct = Food & Wine, which would be fun, but is an extra cost and crowded)
You can also check out http://www.touringplans.com which is a subscription service with TONS of great info like crowd level calendars (they employ a full time statistician), and touring plans to hit as many rides as possible with as little a wait as possible.