Next, we needed some business ideas. After ten years in management I still never knew what anyone was supposed to be working on. Once in a while I would walk around asking everyone what they were doing, and half the time, my reaction was "why the hell are you working on THAT?" So one of the teams started working on finding better ways to keep track of who was working on what. It had to be super simple and friction-free so that everyone would use it, but it had to be powerful, too.
We had an early idea called FIVE THINGS. Everybody would have a list of exactly five things that they were allowed to work on. The top two were things they were actively doing right now. The other three were things that they would do as soon as they finished the first two. But nobody was ever allowed to have SIX things assigned to them. If you have too many things on your to-do list, your motivation tends to sag.
Five Things wasn't the right idea, but it led us to the idea that became Trello. Pretty soon we had four programmers and two summer interns working on it. We started dogfooding the product when it was only 700 lines of code, and even in that super-simple form, we found it incredibly useful. By the end of the summer we realized we had a hit on our hands: an incredibly simple, easy-to-understand way for teams to collaborate online.
Via Announcing Trello