An idea I had 5 years ago was related to local (social networking, news, events,classifieds) - at that time local wasn’t the hot topic it is today (and Facebook was just for colleges).
How did I came up with that? I had a need - I was a fresh immigrant to US (coming from Eastern Europe) - didn’t know almost anybody - and I though would be nice to have a local site for each neighborhood (based of the zip code level) where people can interact, post local news, local events, local classifieds.
I even start coding and did a prototype in the free time I had, and I almost 1 year (which is still online at http://www.mirceagoia.com/local ) hoping that I may present that to an investor - well, I was too new here and I had to look for a job eventually, to survive. So, i abandoned the idea - but, who knows, that idea could be still viable, especially nowadays.