Blanket Forts! Kids will play here for hours! Give them a flashlight, some books, a cd player and CDs.
An Empty Milk Carton and Some Puffy Pom, Poms?! Kids will love putting them in the hole of the milk carton. This is also great for developing fine motor skills. (Keep an eye on young children who might pop these in their mouths).
Walk the Line! Tape a line on the floor. Walk across it, then have your little one try. They will love attempting to stay on the line, and it will help them develop their balance more too.
Dance! Put on some music and dance with scarves!
Play Along Percussion Set! Create a box of percussion instruments out of household items (pots, pans, tupperware bowls, wooden spoons, dried beans in a small sealed container, what else?) and play along to instrumental music!
Indoor bowling! Put some objects on the floor and roll a ball to try and knock them down. I suggest using a "Gertie" ball like we do in music class. It's non-threatening, safe and won't cause harm to the house!
Cardboard boxes! Kids love climbing in them. You can use several and make a train. I suggest making a craft out of it and decorating the boxes with markers, crayons, gluing scrap paper, etc.