Working in Finance shouldn't prevent you from working in a startup.
I can recommend trying to scratch your own itch(es) - are there any problems in particular that you run into on a frequent basis, for which existing solutions are poor and you feel could be done in a better way?
Another exercise I could recommend is to ask yourself what would you be doing now, if you were free to work on anything?
There you go. How would you go about this? Social network? Forums? Magazine? All of the 3 and more? What about monetization? Don't worry, just being a bit rant-ish, I know those are tough questions.
There you go.
I would recommend asking a few outdoors friends whether they feel the same, and see if bringing about this worldwide directory would be a great thing to them.
To me, it sounds like a great opportunity because you have a specific audience to interact with, and there are opportunities to turn it into a business; think of outdoors venues and outdoor equipment companies who would want to promote their products and services to that range of people.
I would recommend asking friends, and in terms of further research, I recommend 2 books: Founders At Work by Jessica Livingston, and The Lean Startup by Eric Ries.
Go for it!