To start the Echo Isles quests, you want to talk to Vanira, who is right next to Voljin in the Sen'jin village in Durotar.
To start the Operation Gnomeregan quests, you want to talk to High Tinker Mekkatorque, who is located in the Tinker Town district of Ironforge.
These quests are counting towards the Loremaster achievement.
More information on the event:
- Official Gnomeregan and Echo Isles announcement and information
- Operation Echo Isles / Zalazane's Fall: Transcripts and details
- Operation Gnomeregan: Transcripts and details
- Echo Isles / Zalazane's Fall quest summary and gallery
- PrintWarcraft.com offers original WoW posters