|CC licensed content portal: http://flickr.com/creativecommons/|
|CC licensed content feed:|
|Approximate size of the CC-licensed collection: 43141737|
CC-enabled search at http://flickr.com/search/advanced/
Size last updated 20070726.
Flickr's choose license implementation can be seen at http://flickr.com/account/prefs/license/ (you must be logged in to a Flickr account).
Flickr's implementation is of the drop down menu variety.