NASA has just released it's 2017-2018 software catalogue, which includes hundreds of free, royalty-free applications for a wide variety of uses.
The catalogue itself is pretty wide ranging, covering everything from drone aerodynamics to video compression. While most of us won't have a ton of use for any of this, there's some broadly useful stuff, including a spacewalking simulator built with Unity and a huge collection of textures. NASA has released their catalogue like this the last few years, but they keep expanding the scope.
You'll find everything in a searchable database over at NASA.