The last few days I have been using the OGR library at work. As the website says, it is a Simple Feature Library. It allows you to rather easy read, manipulate and write vector features in different file formats (for example DXF or SHP).
This can be very useful, as you do not have to create your own file format parser, as I did for my DXF2SCA tool. And the manipulation of the vector data is really nice. At work we for example use the union function to make one big polygon out of different taxiway segments. And the buffer function is used to calculate a grass area around all features of an airport. This way we can rather easy make some generic airports for our visual databases.
I think I will also give this library a try for my next (updated) version of DXF2SCA. That could certainly save me some coding and allows me to focus on the scenery output for FS, instead of reading a certain file format.