I will vote up suggestions that estimate some utility function value for the proposed projects.
E.g. Lives saved per programmer hour or 10 -9 percentage points chance increase of a positive singularity .
Your reasoning can be indirect, e.g. a simple successful project will encourage future hackdays that can potentially reduce the chance of X existential risk by 0.01%.
So, the London community is arranging a Hackday where some of us will get together and code. In order to ensure we work on the awesomest idea(s) possible, we decided to ask LessWrong to add to our list of candidates. So here is the question:
What could a few developers do in a day or less worth of coding that will be awesome? Also, as a way of checking calibration, you can give your estimate for how long such a thing would take to build.
Note: While we will take ideas and voting here into account, there is no guarantee that we will actually end up choosing one or more of them.