The Austin API Hackday was a successful event where teams were given a short amount of time to create innovative projects using APIs from various companies. The three standout projects, "The Application Trail", "Crapcha", and "SMScal", showcased creative solutions to real-world problems. These projects utilized APIs such as Mashery's access, Infochimp's Geo API, Twilio API, and others to develop unique applications that solved issues like navigation, Craigslist ad filtering, and scheduling reminders. The event demonstrated the power of collaboration and creativity when developers come together with a clear challenge and the right tools.