NASA has published its annual catalogue of free software, containing a mix of ultra-technical code libraries and tools as well as some fun apps and utilities.
Most user-friendly is a Spacewalk game (http://www.nasa.gov/multimedia/3d_resources/station_spacewalk_game.html) where you can simulate EVA (Extravehicular activity- spacewalks to you or me) conducted by astronauts on the ISS (that’s the International Space Station, and if you didn’t know that one you should maybe stop reading now).
NASA also has a large collection of 3D models, images and textures (https://nasa3d.arc.nasa.gov/) free to use for education or personal purposes, whether it’s to teach the kids some science or just brighten up your desktop.
And speaking of education, budding astronauts can take a virtual of the Glenn Research Center: The Early Years (https://itunes.apple.com/us/app/nasa-glenn-research-center/id562903295?mt=8) on their iPad, or get the latest Space Weather before your interterrestrial trip.
And once you’ve mastered all; that space science, you’ll be ready to adapt some of the more techy stuff available - control en-mass a flock of drones with the Formation Flying System for UAVs and Satellites (https://software.nasa.gov/software/MFS-33193-1); see the earth from space with the Worldview Satellite Imagery Browsing and Downloading Tool (https://software.nasa.gov/software/GSC-17111-1), or browse through a constantly updated worldwide database of natural hazards like fires, storms and earthquakes with HazPop (https://itunes.apple.com/us/app/hazards-population-mapper/id1092168898?mt=8).
You can see more at the NASA website.