http://www.seeyourhotel.com - Hotel locator with Google Maps. We (2 guys) did it in 2006 and added some features here and there. It's still making money, but we haven't added to it for more than a year.
So its all just affiliate revenue from the hotel bookings?
For the revenues yes, it's just affiliate revenue. At first it was a huge job to clean up the data for the locations. Back then about half the hotels had errors in their locations.