The Cloudmade Geocoding Node.js library by Joshua Thomas supports Cloudmade's Geocoding API. Features of this API include conversion of addresses into latitude and longitude and the use of cloud engine to obtain directions between two different locations. This library includes JSON usage, HTML retrieval, and API key generated parameters.
When we search for information on a map we tend to be searching to find where something is now. But, what if you wanted to find out where something used to be? What businesses used to be located at a particular address? Where did somebody used to live? Where did all the blacksmiths used to hang out? If you are interested in find out that information there's now a solution: AddressingHistory. AddressingHistory is a recently launched web app and API that provides access to historical data consisting of digitised Scottish post office directories combined with maps from the same time period.
There are any number of questions that can be answered by Wikipedia, but you can add "where am I?" to the list. Given any latitude/longitude coordinates, the WikiLocation API will find you corresponding Wikipedia articles to tell you about your surroundings.