Hackathons are all the rage these days. And how could they not be? When cities host the events, they invite computer programmers and software developers to use their open data to work together and create new applications and visualizations around that data.

Iin 2012, for instance, more than 200 data scientists from more than 10 cities around the world spent 24 hours in London designing solutions to help improve the U.S. Environmental Protection Agency’s (EPA) Air Quality Index. Over the years, Denver, Colo., Joplin, Mo., New York City and Reno, Nev., to name just a few, have hosted such events.

And on Saturday, Feb. 23, cities all over the world hosted hackathons in conjunction with the 2013 International Open Data Hackathon. In all, 120 cities around the world participated, some of which are plotted on the hackathon map above.

No matter the location, the goal was the same, according to the Open Knowledge Foundation, which hosted the event: "to write applications, liberate data, create visualizations and publish analyses using open public data to show support for and encourage the adoption [of] open data policies by the world's local, regional and national governments."

And local governments came up with some great projects.

In Austin, Texas, participants focused on four main projects, one of which was a recycling pickup app that would collect recycling and trash pickup routes and schedules, and build out an application that will answer such questions as, "Is my recycling pickup this week?" and "Is my trash pickup day changed because of a holiday?" for a given location.

As reported in The Atlantic Cities, hackers in Oakland, Calif., plotted the city's crime data as a per-day heat map from 2007 through 2012 (deep red means no incidents; dark green signifies more incidents):

In Toronto, Ontario, Canada, hackers worked on showing how citizens' tax money is spent. The participants worked in conjunction with "Where Does My Money Go," a site was that first developed in 2007 to "promote transparency and citizen engagement through the analysis and visualisation of information about UK public spending."

And in New York City, there were many areas of focus. But the largest was on the Occupy Sandy Data Project -- in this stage, participants worked "to collect, digitize and pre-process data that includes canvasing forms, Amazon registry records and more," according to #OccupyDataNYC. At the end of the day, the group applied for an Open Data Commons Open Database License so that Occupy Sandy data can be used to inform civil action, community initiatives and research more broadly.

NYC is taking the work done at the International Open Data Hackathon to the next level on March 1st and 2nd. During its Occupy Data Hackathon, the group will use the data it collected "to help assess the breadth and depth of the Occupy Sandy relief effort, and the extent of unmet needs in neighborhoods devastated by Sandy."