w berlinsearches Wikipedia,
gm new yorkopens Google Maps with New York
gd new york, washingtoncalculates a route with Google Directions from New York to Washington
You can add your own keywords and share them with others. Currently, 6000+ shortcuts are available. Namespaces allow localization of the shortcuts. All shortcuts can be downloaded in JSON format (Creative Commons BY-SA license). Browser integration works with an Opensearch plugin.
Watch a screencast on how to get started: