There are several awesome opportunities out their for putting your Viz skills to the test while creating something that might have real world impact.
One awesome one supported by Tableau is the Tableau Foundation. Who work with several organizations around the world, such as PATH, to help tackle modern day complex issues. From creating plans to tackle issues with Malaria in the developing world to helping visualize the plight of the Cheetah.
More information can be found below for volunteering:
First, check out the #MakeOverMonday series, that has weekly challenges for taking data and displaying it in new and visual fashion.
Another awesome place to do good with data is the Viz for Social Good project. Which allows people to volunteer to help create Vizzes that help support a project that is bettering the world!
There are a few other options out there as well:
Hope this helps!