Larry Ferlazzo's Website of the Day has been around for quite a while. I've never looked to closely at it. Many of the posts are geared towards teachers of English Language Learners, but this post caught my eye:
The Best Online Sources for Images
I usually use Google Image search to find images for my classroom, while I realize that the use of those images may not be completely legal, but it is what I do. The nice thing about this post is that these images are completely free for education use.