OneGeology is a new web site with the mission to "Make web-accessible the best available geological map data worldwide at a scale of about 1: 1 million, as a geological survey contribution to the International Year of Planet Earth." It's an exciting endeavor and one that might mean more data and easier to find data on the Internet.
The effort is to accumulate a comprehensive list of available WMS servers and make those servers available through their portal. They are currently (as of today) claiming 94 participating countries, including many that are already making data available.
They are also working to adopt and encourage the use of GeoSciML, an XML representation "representing geoscience information associated with geologic maps and observations." By encouraging not only the visible data, but making that data more transparent and homogenized, they may just kick-start moving more useful data on line.