Florida Education Technology Center hosts two great resources for educators and students looking for clip art and pictures for classroom projects. One of those ClipArt and so on and the other Clippix etc.
ClipArt ETC is an online catalog of over 70,000 pieces of clip art that students and teachers can download and use in classroom projects. The catalog is arranged into thematic collections and sub-collections. Just choose a group and then a sub-group to find the clip art you want to use. Clip art is available in three file sizes to meet most needs.
Clippix ETC is an online catalog of thousands of images that teachers and students can download and use for free in their classroom projects. Like ClipArt ETC, Clippix ETC is arranged into thematic groups and sub-groups. Images are available in three resolutions to meet most needs.
Watch this short video For an overview of ClipArt ETC and Clippix ETC.
It is important to note that these sets were created specifically for classroom use. This means that you should not come across any images that are not appropriate for school. This also means that the clip art and images license is for classroom use. Use outside the context of a classroom setting requires purchase of a license to reuse images and clip art.