Choose a color (or more) and it loads images with that color scheme from Flickr. Great if you're teaching color and making collages or if you just want color coordinated wallpaper
Great tool to make image searching quick. The Flickr images it pools all come from the Creative Commons area, but I would still check.
Draws from wiktionary, flickr, google & yahoo images.
Searched for "dirty" stuff and it wasn't too bad or concerning.