GooseChase - The Original Scavenger Hunt App
Ideas Grab - A list of +3400 ideas that you can get for your projects.
Actionbound - Take people on real-world treasure hunts and guided walks Actionbound is an app for playing digitally interactive scavenger hunts to lead the learner on a path of discovery. We call these multimedia based hunts 'Bounds'.
The 25 Days of Ideas - Free resources for coming up with startup ideas
Scavenger - An augmented reality scavenger hunt for cash prizes
Validated ideas - List of 5,000 poorly executed but popular apps