Does anyone have a recommendation on a demographic database or API? I have found one here http://demographicmarketing.net but I was looking for more options. I like that they have a lat/long and IP Address lookup built into the API.
Take a look at QGIS & GRASS for a number of APIs for accessing geographic based data and some of the data sources listed here for a number of gratis data sources including demographic information. There is also a very nice tutorial here on accessing geographic demographic data.