Well, I have to think anytime is a great time to visit WDW! However, if you'd like to avoid the crowds and have better room rates, Disney has actually identified those time periods. Simply click
here. The basic rule of thumb is to avoid visiting during traditional school breaks. Also, I'd avoid August because I simply cannot imagine the extreme heat. We just returned, and it was already mighty muggy, steamy, and hot. A couple of cast members just chuckled and said this is just the warm-up for what is to come in August - yikes!
With all that said, my hands-down favorite time to visit is during the first few weeks of December when Disney is absolutely dressed in its absolute finest, the weather is mild, and the resort rates are often at the lowest.