this is a fun place to poke around in for a while. Also, your Art teachers, or classroom teachers might find a good site or idea here. Not all the links are necessarily good for the classroom, but there are certainly a great many discussion starters listed. Take a look.
"Welcome to the Coudal Partners Museum of Online Museums. Here, you will find links from our archives to online collections and exhibits covering a vast array of interests and obsessions: Start with a review of classic art and architecture, and graduate to the study of mundane (and sometimes bizarre) objects elevated to art by their numbers, juxtaposition, or passion of the collector. "