Druids in Wrath of the Lich King have 71 talent points at their disposal, just like any other class at level 80. These points can be spent on the talent trees Balance, Feral Combat and Restoration. Druids are the only class where the distribution of those talent points makes such a big and noticeable difference though, as the whole playtime changes with the talent point allocation.
A special feature is that there are even two ways of spending the talents in the Feral Combat tree, making for a total of 4 different roles a Druid can fulfill.

A Druid spending points in the Balance Tree will be able to cast powerful spells to damage his enemies from a distance. He will learn the special Moonkin form, which amplifies his offensive spells while making him unable to cast heals.

The Feral Combat talent tree allows that Druid to specialize into one of his two animal forms. As a cat he is able to deal substantial melee damage similar to a Rogue while a bear Druid makes for an excellent tank.

Restoration Druids spend their talent points to enhance their healing spells. A Restoration Druid even learns the Tree of Life form that amplifies their healing output while preventing them from casting any offensive spells. The Tree of Life aura even increases healing on anyone affected by it.

There are of course some talents in the lower tiers of every talent tree that are attractive to the Druids of the other specs. This allows for some variety among the talent specs. An example for such a talent would be the Master Shapeshifter talent, which gives a bonus depending on your current form.