WDW?
 

Looking to book a trip (Summer) and trying see if any one month is less crowded than the others? We've been a few times but always in late Jan./early Feb. and crowds were never an issue.

As early as possible in June (or may if possible) the longer schools are out the more crowded it gets. (and hotter!)

I was thinking also about the weekend & partial week before Memorial Day Weekend (5/20-26). Is that considerably better than June, July, Aug.? I ask because we were originally looking at going early-mid August.

Your Memorial Day timeline is MUCH better than August! August is our hottest, most humid time, full of terrific thunderstorms (we are the lightning capital of the U.S.). May is the last of the drier season, and it starts to get rainy during the end of the month, but you should still be OK. Remember, as swalter518 advised, once the schools are out, you are in the crowds...

Pumpy, we have been to WDW quite a few times the last week of August. Advantages: Florida kids are back at school, the fall slow-down in attendance is beginning and crowds are less. Disadvantage: It is hot! However, I live near Richmond VA and July and August here are like steambaths when you go outside! I enjoy the daily afternoon thunderstorms in orlando.