Just like every other class the Priest has received new spells with the Wrath of the Lich King addon. At level 75 a Priest is able to learn Mind Sear. This is a channeled spell damaging any enemy target near the spell's target. This marks the first effective AoE-spell in the Priest's arsenal, as Holy Nova was far from fitting that description.
At level 80 a Priest will learn Divine Hymn. While this is a situational spell it is able to become a powerful weapon if used correctly. No matter if it's lots of enemies in PvE combat or a single target in a PvP showdown, this spell is able to keep an enemy at bay. Despite these new spells Priests got access to several spells which were racial Priest spells or talents prior to Wrath of the Lich King. Holy Nova falls into this category, a spell that damages enemies and heals friends in a small area around the caster. Devouring Plague used to be available only to Undead Priests. This damage over time spell can now be learned by any Priest.
The other sources of new spells are the new ultimate talents in the various talent trees. Discipline Priests get Penance, which can be used as an attack or healing spell, depending on the target of the Priest. This spell is channeled over its 2 second duration. If talented and used as a heal this will also reduce the incoming damage for the target for the next seconds. The Holy tree received the Guardian Spirit spell, a spell that prevents a fatal hit on the target it is cast upon for the next 10 seconds.
The Shadow tree received the spell Dispersion, allowing the Priest to regain up to 36% of his mana while not being able to attack. Additionally his incoming damage is reduced by 90% when using this spell.