It depends. I highly recommend The Unofficial Guide to WDW, which has (among a bazillion other cool things) a spreadsheet of how long it takes to travel from each resort to each park.
Depending on which resort you're staying at, it generally takes between about 20-40 minutes to travel to the parks. Resort hopping is a whole 'nother beast, though. With the exception of the Bay Lake resorts, you'll have to go from your resort to a park, then transfer to a bus going to the resort you want to visit. One option is to take a break from the park at lunchtime and hop the bus to a resort for lunch. For the Bay Lake resorts: the boat connects MK, WL, FW, and CR. The Monorail connects MK, Poly, and GF--and Epcot, except you will have to transfer at the TTC.
From Port Orleans, you can take a boat to DTD. I *think* there's boat service from DHS to one of the resorts as well, but I'm not sure which one. HTH!