Question: Im developing an application to print flight paths on a world map.

To do this i need a dataset to describe the latitude and longitude of various coastlines (and country borders if possible) of the world so I can plot them.

Is there anywhere on the web I can find this kind of data? (preferably free/cheap)

Thanks!

Answer: 
Check out <https://osmdata.openstreetmap.de/> from Jochen Topf. The data has been derived from OpenStreetMap ways tagged with natural=coastline. See also the data update.
GSHHG is definitive your first choice, but depend on the scale you need take also a look at <http://www.naturalearthdata.com/>