Put real spiderwebs on paper. preserve a spiderweb on paper to explore/look at. or put the black paper behind it so it can be seen in detail and then take a picture so you don't have to destroy the spider's web.
this is one of the best water wall ideas i have found. really simple and lets kids turn the bottles to direct water different places. also keeps bottle caps to stop water! i am going to try this and use other containers too! would work well on wood too.
Yo-yo painting--this looks so fun Fill a cut-off stocking with dry beans (I'll probably use rice, because that's what we have). Dip it in paint, then pretend it's a yo-yo and bounce it on a piece of paper. So fun!