One of the best resorts to get fresh fruit at is Coronado Springs' Pepper Market. The others have some limited prepackaged fruit, and most will sell bananas in the am (though they sell out!). PM has an actual fruit/sandwich/salad station with live staff preparing fruit.
In the parks there are fuit stands with some fruit - Liberty Square in MK (near HM), Near Haramabe Market (Africa - just outside the safari ride) at AK, the food court at MGM near the BB show. Selections vary.
Fresh cut fruit is one thing that's sort of lacking a little at WDW, IMO. It's one of the things we always stock up on if we get a chance to go to a market.
Some of the buffets offer whole apples and oranges - CM and CP come to mind. I think fresh fruit was also available at the character breakfast buffet at the Swan -but they are remodeling. The new Med Market at the Dolphin advertises their fresh fruit juices.
Nowhere I have seen recently on property - FLORIDA oranges. They are all Sunkist from California - Yuck!