Google has just launched a "Usage Rights" category in their advanced search. It uses Creative Commons license to allow users to search for works which either "allow some form of re-use" or "can be freely modified, adapted or built upon". This is a great step forward and will hopefully increase the adoption of Creative Commons (CC).
On the other hand, I don't see CC mentioned on the page and having only two choices is limiting, considering the various other licenses that people are likely to use. Yahoo advanced search already has two radio buttons instead allowing you to choose "Find content I can use for commercial purposes" or "Find content I can modify, adapt, or build upon". This actually allows three choices (depending on how you count) and they have a CC logo and a link to an explanation.
I realize it takes a lot for Google to add this and I appreciate all of the work that went into getting this done. Yahoo and Google are both probably testing this feature to some extent. It would be great if you could all spread the word, try to service and give feedback to Yahoo and now Google so they continue to integrate Creative Commons into their offerings.
In addition to Google and Yahoo, there are many other services that have begun integrating Creative Commons. See the web page for more info.