Link: Yotophoto | Find free photos... fast!. This is a search engine that indexes over 250,000 images from Flickr, Wikipedia, Stock.Xchng, Morguefile, Pixelperfect Digital and OpenPhoto. Their mission as they put it is "to help people locate, remix and republish open and copyleft images. We aren't just about 'free stock photos' for designers, but also about helping educators, bloggers and digital artists find photos they can use without fear of "the man"."
Search functionality is fine - the advanced box is all/any words, exclude words, image licenses (CC, GN, PD or Site Specific), dimensions, orientation, color. The results were reasonably accurate, although several of the images that I got as a result of my searches linked me to Flickr images which were not in the public domain at all (although this was the exception.) There was no 'family filter' available, so I did a few of the obvious searches and didn't turn up anything objectionable, so I reckon that they've got that pretty much covered.
If you're looking for a quick source for images that you can use on a site/blog/whatever, this looks like a good resource to use - just double check on the rights to make sure.