I recently participated in my first Startup Weekend, held in San Luis Obispo. My friend and I joined Project Orange, which was later renamed to Karmik. Our goal was to create a website that allowed users to trade favors -- for instance, 'if you wash my car I'll cook you dinner'. I was put in charge of website development. I quickly taught four other fellow developers about Ruby on Rails, and then assigned them all tasks. I ended up providing oversight and architectural decisions while implementing Elasticsearch support myself.
At the end of the competition, our group decided to not continue the project. You can find our project on GitHub.