Pick up a copy of the Unofficial Guide - the crowd calendars are in there and it is packed full of other useful info - it'll keep you occupied on the journey to WDW too
The Unofficial Guide to Walt Disney World 2008 by Bob Sehlinger and Len Testa is the one that we have and it's awesome. You can access the crowd calender for this month free at their website, (google touring plans). If you have the book, you get access to upcoming months information. I've already used their calender for May to make our touring plans and plan our ADRs. It's a big book, but very helpful.