The Polynesian and GF both have boat and monorail service to the MK. The CR has a sidewalk that runs between it and the MK, as well as using the monorail. All three resorts use the monorail to get to Epcot. Buses go to all other areas...DTD, DHS, AK, water parks.
BW, S/D, YC/BC all have a boat that connects them with both Epcot and DHS..as well as a walking path. There are buses to all other parks.
The values and moderates all use buses to get everywhere...except for POR. You can get a boat to DTD from there.
OKW and SSR have boats that go to DTD, but buses everwhere else.
WL and Ft. Wilderness have boats that go to MK, as well as buses. And buses everywhere else.
AKL has buses everywhere.
It can seem confusing but once you get there, it's all very easy to figure out. There is very good signage to direct you. If you have any doubts about buses, just walk up to a bus that is loading and ask the bus driver whatever it is you need to know. Do not depend on your resort CMs to know how to get from point A to point B at WDW. Ask the bus drivers or boat pilots.
The buses are supposed to arrive every 20 or so minutes to get you to, and from, the parks.