Gowalla said a writeable API was coming soon. Today, the check-in API is available to developers. Though it took longer than anyone expected, the announcement and the API have some nice aspects to help developers use the new features.
Wikimapia is a web service that allows users to edit information on a world map in a wiki format. Users of the site can add places, edit them, and get the information previous users have entered. The info there is currently pretty sparse, but the service is rather new. The company also recently released a Wikimapia API that supports getting information from the web service.
With roughly one-third of our entire mashup directory composed of mapping mashups, we've come to expect a lot if a site plans to use a map. That said, we're still big fans of maps and are always excited to see something new. Each of the mashups below brought something new, whether it's interaction, data, visualization--or all three.