Don't forget to balance the value of the dragon's corpse with the other treasure they might pick up from the dragon's horde. If the dragon's horde is not readily available, then I would up the value of the corpse for use as spell components or material for magic items, even if you don't get specific (just say dragging the corpse back to town would be worth 1,000 gp in parts and leave it at that)
if you want to brainstorm ideas, though, here are some of the top of my head:
Blood/Bile - useful in potions, especially dragon breath, heroism, acid resistance. Drinking it might also be a prerequisite to entering certain prestige classes. Useful as ink for spellbooks and glyphs. Also, normally potions only can be crafted for 3rd level spells and below, but dragon blood might remove this limitation.
Meat - when properly prepared and eaten, functions as a hero's feast. Also valued by the nobility as a delicacy.
Claws/Teeth - even when not used as weapons, still make useful hilts for weapons. Decreases the cost of the enchanting the weapons as long as the enchantment relates to dragons in some way.
Horns - (if the dragon had horns) can be hollowed out and be useful as a musical instrument
Hide - pretty much what everyone has listed so far, but even the scraps can be made into "accents" on other armor, shields, or boots or as a fashion accessory. Dragonhide boots might be highly fashionable among the nobility. Offer a discount to enchant it with DR or acid resistance. A taxidermist might mount the whole thing as a piece of art suitable for a throne or trophy room.
Bones - aside from bone armor (not sure what book that was from), grind them up into powder for potions or more likely use this for wands, rods, and staves. If carved very carefully, could be used for easily-enchanted rings and other jewelry.
Skull - can be crafted into a helm if sized appropriately. Also valued for the prow of a ship or for mounting above a hearth. if the jaw can be opened wide, it could be suitable as the frame of a mirror or painting.
Wings - aside from their use as hide, also valued as damage-resistant sails for ships. (A ship with red dragon-wing sails would be less concerned about fire.)
Tail - aside from their use as hide, also valued as a whip or as a staff (if made rigid)
Eyes - valued for divination magic. A dragon eye might serve as a core of a crystal ball, or be otherwise hardened and mounted atop of staff or on the pommel of a weapon as a material component. Also may be prepared and eaten as a potion of true seeing
Brain - valued for Intelligence enhancing items, or ground up and used for ink in spellbooks.
Heart - valued for love potions and potions of heroism
Genitals - valued for love potions, as an aphrodesiac, or as a cure for sexually transmitted disease
Entrails/Organs - may be ground up and fed to cattle for increased yield, or mixed with grain and fed to horses to breed especially hearty warhorses. May be buried in a field to increase crop growth.
Milk - (if a female dragon) good for potions, especially healing and restorative potions. Similar to blood (see above).
in addition, superstition may add value to any particular parts beyond their material value. If the locals believe that mounting a dragon-skull above their fireplace will grant good luck, they will value the skull more than if it were just as a decoration.