Activities for Siblings during Homeschool

This is one of the most common questions for new homeschooling parents (like me): What do I do with the younger kids while I teach the older ones? I've been collecting some great resources that are making our school time richer and more fun (with special thanks to my big sister Christa). I give the sibling activities in the same subject as the other student (its not always the older one!). The activities are so much fun, that the other child often joins in when their lesson is finished!

I have tried really hard to find free activities or printables that stand alone, or complement some of the manipulatives and materials I already own - so if you don't own some of these, you may have to invest in a few good materials. Also, the activities need to be fun for many many sessions, not just once or twice, and something the child can do without a lot of supervision. Print and laminate (if you can) printables ahead of time so you can pull activities out as need. Below is my list of ideas and activities for siblings during homeschool.

Math
We already own lots of manipulatives from Right Start Math and goodwill, so finding good printables and ideas is a great way to use that investment, and prepare them for formal lessons later.
Pattern Blocks and free printable activities from learning resource
Cuisenaire rod and free printable games
Geo-boards and printable shape patterns

Reading/Grammar
Keeping fun, special use books and games on hand makes learning to read feel really special - and Bob books are definitely a favorite around here!
Bob Books and free printable activities from by Bob Books and more from Royal Baloo
Independent Reading for older kids with my reading chart
Sight Words flash cards games (make up sentences with cards, or read through and make piles of "words I know" and "words I don't know")
Explode the Code books

Literature
After we read something together, older children sometimes have to do a writing activity following the reading. Younger children can muse on the story by recreating scenes with special materials reserved for this time. The special materials and story prompt  keep children focused.
Modeling Clay like plastillina - encourage them to mold shapes on their own with out extra colors
Drawing with special materials like Beeswax crayons

Coloring and Puzzle Printables
There are tons of free printables online, but finding really great quality coloring pages and worksheets from thoughtful designers is always a bonus. I print lots of these and keep them in a folder, only giving one at a time so each page is valued.
Made by Joel printable Coloring Sheets and Worksheets
Mr. Printables Puzzles and Coloring
Fancy coloring pages from D. Palmer

Do you have more resources to add?