As far as I can tell, you can't quickly search Flickr for "all creative-commons images" - just individually by the three licences that Flickr supports.
So, this form will just stop you having to dive into that 'advanced' setting every time you want to play.
:)
Additionally, here's a (non-CC-filtered, sadly) link to today's most interesting images...
http://www.flickr.com/explore/interesting/2008/05/15/
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