Hi Jaimey, this is an interesting question because it cuts to what I believe is the next phase of the open data discussion which is, "open data, to what purpose?". Perhaps this should be the first phase but I'll leave that alone for now.
Daniel hit the nail on the head the the second para of his post; "you have identified a service that you believe will be beneficial to your citizens, instead of your citizens coming to you asking for this service".
Open data can be seen as the answer to a question no one has asked. So the magic is finding existing, substantiated citizen needs that can be addressed with the judicious use of open data. You also mention making it available in a format "we" can use. This begs the question; is there an internal operational or strategic need that supports your case?
Ideally both needs exist. Find them and then look for similar (don't have to be exact) examples to support your argument.
I fully support Daniel's idea to identify needs from outside groups, particularly ones that have an economic influence in the community.