In Greek drys signifies 'oak,' from an Indo-European root *derew(o)- 'tree' or 'wood.' Thus dryads are specifically the nymphs of oak trees, though the term has come to be used for all tree nymphs in general.
Family
The nymphs of ash trees were called the Meliae. The ash-tree sisters tended the infant Zeus in Rhea's Cretan cave. Rhea gave birth to the Meliai after being made fertile by the blood of castrated Ouranos.
Powers/Weaknesses
Dryads, like all nymphs, were supernaturally long-lived and tied to their homes, but some were a step beyond most nymphs. These were the hamadryads who were an integral part of their trees, such that if the tree died, the hamadryad associated with it died as well. For these reasons, dryads and the Greek gods punished any mortals who harmed trees without first propitiating the tree-nymphs.
See also the myth of Daphne, who was pursued by Apollo and became a dryad associated with the laurel.
Dryads are units of Wolf clan of the game wikipedia:Battle Realms WotW. They attack by using light-sabers..
Dryads are featured in the World of Warcraft game, seen mostly on the continent of Kalimdor as allies of the Alliance and Night Elves. They appear to be half deer, half elf. [1]
Dryads are also featured in wikipedia:Dungeon Siege II as a selectable character race. They are a part of the story and live in tree-towns. They look like humans except their greenish skin colour.
Dryads appear as servants of the Trickster in the Thief series.
A dryad appears in Runescape as a woman with what seem to be twigs growing out of her.
Dryad is wikipedia:Monster in My Pocket #70, resembling a hamadryad, or the Dryad outfit that Penguin wore in an episode of wikipedia:The New Scooby-Doo Movies. There is also a large inflatable version of the character that was available as a Spaghetti-Os premium.
In Warhammer, Dryads are the vengeful spirits of trees and are able to shape shift into different forms, but generally appear as unearthly, lithe and beautiful maidens. In battle, the Dryads take on their war-aspect, with distorted limbs, features and vicious wooden talons capable of rending and impaling their foes.
In the trading card game, Magic: The Gathering, there are some creatures with the type Dryad, mostly in the color Green, many known for their ability to "walk through" a particular type of land. (Most commonly a forest, but sometimes other types of lands as well)
A Dryad is featured in episode 3x01 of the Australian children's television series wikipedia:Round the Twist, impregnating one of the (male) main characters.