MasterGo
A commercial Go database program designed for searching patterns, such as when studying Fuseki and Joseki. The database contains 50405 professional games in a proprietary format (as of March 21 2010). Updates are available to all registered users.
Main site: http://www.MasterGo.com/mastergo
Demo version: http://www.MasterGo.com/downloads/mastergodemo.exe
Distributors
The MasterGo website gives Slate and Shell as distibutor for North America and Schaak en Gowinkel het Paard and Hebsacker Verlag? as distributors in Europe, but only Hebsacker Verlag? mentions MasterGo in their catalog:
Direct link (in German): http://www.hebsacker-verlag.de/product_info.php?cPath=59_15&products_id=75
Curious: It is mentioned as New and also as "Dieses Produkt haben wir am Wednesday, 30. June 2004 in unseren Katalog aufgenommen" This product is added to our catalog on Wednesday, 30. June 2004) and is confuces Mastergo and SmartGo in the description.