Re: I use .internal
I actually use .int myself, for the same reason, with the additional catch that it's three letters. The fact it can also be easily confused with a common shorthand for integers makes me think it's an unlikely TLD to be registered.
PS. Only NOW do I learn that .int is indeed reserved. Good news is that it's intended for true international agencies and that the application process is incredibly strict. End result: I probably haven't stepped on anyone's toes in the process. I'll change the internal TLD later.