And mind you, Dragon Mount (Draconomicon) only gives you a dragonnel as a special mount. You can get a special mount dragon even without this feat, with options including dragonnel, wyvern, spiked felldrake and bronze/silver/gold dragons.
Me? I took a page from the variant special mounts section in the DMG and allow a paladin to have (effectively) a half-dragon warhorse as a special mount (reduce the effective paladin level by 3 for these purposes).
Oh, there's also the drakkensteed in Dragon Magic,