Disney's Magical Express gives guests a free shuttle to their Disney World resort. When guests arrive at the airport, they head to a special welcome desk and board a "Disney's Magical Express" bus to their resort.* (Guests need to reserve in advance -- read more.)
Guests don't even need to pick up their luggage: before their trip, special Disney luggage tags are mailed out, and the tagged luggage is picked up at the airport and delivered to guests' rooms.
Also: for many major airlines, guests can check in right in the resort's lobby for their return flight home. Boarding passes are issued and bags are checked; guests can then enjoy the Resort until it's time to board the Magical Express bus to the airport. (Tip: this lobby check-in service is available for domestic flights only.)
*Always check for updates!