MK to EPCOT= grab a monorail or ferry to the TTC (Transportation and Ticket center) and from there grab the monorail to Epcot,another option if you plan to enter EPCOT via the International Gateway entrance is to just take a bus from MK to the Boardwalk or the Beach Club and walk or take a boat to the Epcot IG entrance
MK to DHS=monorail or ferry to the TTC and bus to DHS,you could also just walk to the contemporary and grab a DHS bus there or get on the resort monorail to the Grand Floridian or Polynesian and grab a DHS bus there
MK to AK=same exact procedure as for going to DHS,either bus from the TTC or bus from one of the monorail hotels
EPCOT to MK=monorail to TTC and monorail or ferry to MK or exit Epcot at it's IG entrance and walk or take a boat to the Boardwalk or Beach club and grab a MK bus there
EPCOT to DHS=bus to DHS from the front of the park or exit Epcot at it's International Gateway entrance and either walk or take a boat to DHS,never walk the whole way in hot weather it's like a 20-30 minute walk and will tire you out
Epcot to AK=bus
DHS to MK=Bus to the TTC and monorail or ferry to the MK or bus to the Contemporary and walk to the MK
DHS to Epcot=bus to Epcot's main entrance or walk or boat to Epcot's International gateway entrance,again don't walk it if it's hot out,at least not the whole way as you can take the boat to the Boardwalk or Beach Club and walk from there
DHS to AK=bus
AK to MK= bus to the TTC and monorail or ferry to the MK or bus to the Contemporary and walk to the MK
AK to Epcot= bus to Epcot's main entrance or bus from AK to the Boardwalk or Beach Club if you wish to enter Epcot via it's IG entrance
AK to DHS= bus
If you want to go from a park to DTD you have to go to a hotel and grab the DTD bus from there,from some parks like the MK it's easier as you have the Contemporary a short walk away or you could catch the resort monorail to the Poly or Grand Floridian and grab a bus there as well.The same for Epcot as you can exit via the IG entrance and walk over to the Boardwalk and grab a DTD bus.Another option from any park is to take the Saratoga Springs bus and get off at the Congress stop and walk over to the DTD marketplace.From AK for example that's what I would do as the only other option would be to just grab a bus to any hotel and then from that hotel get the DTD bus,it's much easier to just catch the SSR bus and walk over.
Resort to resort transportation is more limited as the only real resort to resort transportation would be getting on the resort monorail which makes stops at the Poly,Grand Floridian and Contemporary as well as the boats between DHS and Epcot which stop at the Swan and Dolphin,Y&B Club and Boardwalk.Any other resort to resort transportation would have to be done transferring at a park or DTD.