There are a lot of secrets out there, and they make wonderful sidequests!
All tagged quests
Questing in the Multiverse - d100 Quests in the Planes
A d100 list of planar quests to bring your party into the multiverse, and beyond!
Have I Got a Job for You - d100 Quests for Tools
100 quests, adventures, and plot ideas to be used for those who use tools.