The Unofficial Guide to WDW has a section about how long it takes to get from place to place using different types of transportation (rental car, buses, boat, monorail).
One thing to remember is that it's hard to go from resort to resort, or from one of the parks (like DHS) to DTD, using only disney transportation. In cases where you're going to resort-hop or if you're going from a park to DTD, I'd definitely recommend traveling by car. There are no resort-to-resort buses or park-to-DTD buses - you would always need to transfer, and that takes extra time.