I don't understand the difference between Creative Commons and Flickr. To me they look like they are interconnected with each other.
Flickr is a photo sharing website which is now owned by Yahoo. One of the features of Flickr is that users can choose to license the images / photos they share using Creative Commons licenses. This has resulted in VERY large collections of Creative Commons images on Flickr, under different licenses. All of these are accessible from www.flickr.com/creativecommons. Click on the "See More" links after each license to view more images and search for images which use just that license.
In our T4T class, we are using the websites Compfight and Flickr Storm to search Creative Commons images. Both these sites (as far as I know) just search for images on Flickr. These sites are more user-friendly and offer good functionality not found on the "standard" Flickr Creative Commons search site. These sites are essentially "search portals" for photos hosted on Flickr, licensed via Creative Commons.
For further reading about the differences between Creative Commons and Flickr, I recommend you read (or scan) the English WikiPedia articles for each organization / entity: