Friendship Bracelets using yarn (easier on little hands.)
Turn fingerpaint works into cards or silhouette art.
Spray paint.
Jar art which I would try with baby food after Miss O starts solids (presuming we buy some canned baby food!) The smaller size of the baby food jars might be easier for little kids, too. And I would skip the black puffy paint part and just let the kids use tissue paper and Modge Podge to make mosaic jars that we could put votive candles in… maybe different colors for different holidays?
Nesting shoebox dollhouse – I’m going to start gathering boxes for that one!

(Fun links from Jennifer’s school blog!)