A hack day is an event where developers, designers and people with ideas gather to build cool stuff – the events now run all over the world. The ‘days’ are generally run over 48 hours. The first day starts with talks about practical matters (how to access datasets and APIs) as well more inspirational matters to encourage developers and designers to think beyond their normal areas of interest.

In Feb 2011, a few of us hosted a Civic Hack Day that brought together Baltimore’s open city data and technologists to build apps for citizens.

Music Hack Day’s are similar events focused on the creation of music tools. Here’s a great video from the NYC Music Hack Day organized by John Britton, a friend of mine that is also organizing an Edu Hack Day in NYC in Sept 2011.