I have a powershell script that is useful for interfacing VSO builds/releases with jenkins. Is this something I can contribute to the community via a wiki or should I post this elsewhere?
If you really want to, you can expose the problem as a question and post your script as a self answer.
It's usually quite hard to write a good question once you have a solution for it, try to think as if you had asked it before writing the script to keep it open enough for someone else to add another answer tackling the same problem.
Quoting the help center about self answer:
If you have a question that you already know the answer to, and you would like to document that knowledge in public so that others (including yourself) can find it later, it's perfectly okay to ask and answer your own question on a Stack Exchange site.
So it's absolutely the way to go if you want to share your script. There's no reason to make the post community wiki for this kind of cases.