Here's a few:
Count the number of windows in the house (or doorknobs, or drawers)
Make a blanket fort with the chairs and tables in any room
Colour blobs of shaving cream (regular liquid food colouring or tempra paints, dry or wet) and 3D finger paint with them --on paper, on windows, on the walls in the shower or the bathtub
Make playdough and then play with it
Cut a variety of shapes out of a book of construction paper, pile them in the centre of the table and hand the kid sheets of paper and glue
Read stories
Make stories up
Play dress-up with your clothes while you sort your closet for the seasonal change
Have a taste-test of all the spices in the cupboard by adding 1/2 a tsp of each to a tbsp of cream cheese or sour cream... make a chart of them and put stars on the ones the kids like best
Make soup
Repot plants
Iron tea towels
Learn to knit
Mix dish detergent into tempra paints, and paint on the windows (the dish soap helps it come off easily later)
Cut paper chains, paper doll chains, or snowflakes out of printer paper and hang them in the windows or from the ceiling
Play with matches -light a small box of them one at a time and let the kids blow them out