I really like the speed and layout of FlickrCC. Simple search field with tick boxes to indicate if you want photos you can edit and/or use commercially. Your search results appear on the left half of the window. Click on a thumbnail and the image appears on the right side of the screen. Attribribution and URL appear with it, along with links to allow you to edit the image in Picnik or on your computer. Along the bottom are links to the other sizes of the image.
I plan use this for myself. However, since it does not have a safe search feature, I plan to use Compfight with students. Do you have a favorite way to locate images in the Creative Commons domain?