I have been working on a new directory type site the last couple of days.
The site is a directory for flight schools in Australia. You can see the site here:
I am thinking that bidding on aviation type keywords should be relatively high. If I can get some traffic to the site, perhaps I could charge for some featured listings.
I have at least one more idea for a directory site. These types of sites should run themselves, new content is created by people visiting the site leaving me with little much else to do once I have put in the time to set the site up.