"GeoURL is a location-to-URL reverse directory" - http://geourl.org
Billed as the GeoURL ICBM Address Server, GeoURL gives web page creators a standard way to attach a geographical location as latitude and longitude to web pages. When a page is indexed by the GeoURL bot, its physical location, name (independent of the HTML <title>) and URL are added to the database and a little red dot is added to the world map on the site's front page. The database can be queried from www.geourl.org to find web pages close to a physical location or one of the indexed URLs. A nifty display mode on the site allows you to see the nearby URLs broken down into 8 compass directions.
Of course the idea is to embed a location which relates to the content of the page, rather than the location of the server that the document is sitting on. The GeoURL site is very blog-oriented, seemingly to give the database more appeal as a community of real people rather than a network of restaurants and Starbuckses. To promote this idea, the news section of the site is done as a blog with an RSS feed and individual feeds are available at the bottom of each page of search results, affording you an easy way to keep track of goings-on in a specific locale.
How do I find my location?
Ideally you'll want your coordinates to 3 or more decimal places to give an accuracy of about 50 metres (depending on where you are on the globe).
In the UK, www.streetmap.co.uk has a tool at:
http://www.streetmap.co.uk/streetmap.dll?GridConvert
which can do the conversion from your postcode.
For USAns there's the nifty ACME mapper front-end to Microsoft's Terraserver at
http://www.acme.com/mapper/
Remember that for this site you'll need to convert your longitude from a positive west value to a negative east one, so W118.40648 would be entered as -118.40648.
For everyone else there's whereonearth's:
http://www.whereonearth.com/demos/geocode/
How should I modify my pages?
In the <head> section of your page add your coordinates thusly (with different content attributes, natch):
<meta name="ICBM" content="40.70324, -73.92807">
<meta name="DC.title" content="humans aliens robots monkeys">
Then just go to http://geourl.org/ping/ and get your page indexed.
What's all that ICBM stuff?
It's a reference to the predecessor to GeoURL: a method of defining the exact physical location of Usenet links. See the Jargon File's entry for ICBM Address.
Sources and further information
GeoURL - http://geourl.org